What Does the “Octane Rating” of Fuel Actually Mean

Unlock the secrets of your vehicle's performance in our latest video! Discover the science behind octane ratings, engine knock, and the surprising history of fuel additives. Buckle up for a fuel-filled journey!
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[@Case16710]

When I was 8, we were getting gas and, out of curiosity, I asked my dad what octane was. My dad’s a biochemist. He spent the next 25 minutes telling me about hydrocarbon chains and cylinder pressures and combustion. It changed my life. I grew up to become a commercial artist.

[@Vee_of_the_Weald]

😂 good man! (You, not your dad - although he sounds like a great dad)

[@David-lr2vi]

😂

[@Case16710]

Thanks guys. Yes, he’s an awesome dad and an even better grandfather. 🙂

[@daveknight3940]

haha, the apple fell far from the tree. but I bet you're passionate about your job, and your father certainly was to go through all of the science relating to octane with an 8 year old. I may be wrong, but if you are excited to go to work, it's because of the way your dad raised you. good on ya, and him.

[@ZhoRZh37]

I studied Applied arts and I'm a designer by profession. But almost all my enthusiasm goes to engineering and maths. I enjoy my job, but I'm not very interested in arts in general. I know the history of visual arts as much as I needed it for my studies. I find more appeal in well designed systems and much more beauty and divinity in mathematics than I could ever see in any of the grand masterpieces.

[@Hypn0s2]

TLDW version; High octane resists igniting/combusting from just pressure. Most cars are designed for low octane. Higher performance cars can be designed for higher octane. Especially turbo charged cars. The resistance of high octane to combust from pressure/heat can allow for more performance by advancing spark timing (making the spark plug, spark later) and such.

[@ulbuilder]

Advancing the timing results in the spark happening earlier, not later.

[@JimAllen-Persona]

I’ve got an even shorter TL/DR version: Octane rating is the percentage of iso-octane in the iso-octane/ n-heptane mix that comprises fuel.

[@tarkov666]

Do not just go using different octane rating... cars are designed for specific ratings for a reason...

[@jeffk464]

Nope, with NA cars you can have a higher compression ratio with higher octane. More compression = more power.

[@blist8329]

Since high school I've been trying to tell my friends that high-octane does absolutely nothing to their stock Toyota Camry. I'm now 25 they still haven't learned

[@bfkennedy]

This is an extremely dense combination of scientific facts, history and associated political interests. I was expecting a simple explanation, but really loved the breadth of this subject. It has expanded my view on the subject from simple curiosity to real interest. Thanks!

[@socallars3748]

I've come to expect nothing less from Simon and his team. Good stuff.

[@ericluffy7970]

Simon Service Satisfies

[@sirclarkmarz]

Short answer, unless you have something like a Lamborghini regular gas is just fine. Just stay away from the ethanol that stuff will screw up your engine sensors

[@carlthor91]

@@sirclarkmarz Unless they are made to work with it. Generally speaking the ethanol is hygroscopic, if you don't use the fuel, it will absorb moisture. This is the culprit, that wreaks havoc with the engine sensors, spark plugs. Our family has two vehicles that use blended fuel, we do not let them sit. No issues, both over 200k km, the pickup is approaching 300k km.

[@MadLadMartyMcFly85]

​@@sirclarkmarzwhen you say regular gas Im not sure if you mean 87 90 93?? Or regualar gas compared to ethanol??

[@aanchaallllllll]

0:50: 🚗 The octane rating measures a fuel's ability to resist engine knock, which can cause damage to the engine. 2:57: 🔢 The octane rating of fuel indicates its performance compared to a reference fuel, not the actual proportion of octane in the fuel. 5:45: 🔽 The history and dangers of leaded fuel and the transition to ethanol as an octane booster. 8:31: 🛩 The aviation industry still uses leaded gasoline, releasing around 100 tons of lead into the atmosphere every year. 11:23: 🔑 Thomas Midgley Jr. is considered one of the most environmentally destructive individuals in history, responsible for the creation of chlorofluorocarbons (CFCs) and the introduction of leaded gasoline. Recap by Tammy AI

[@ambition112]

Beautiful! Thanks for saving my 1hr + time! love this tool Tammy AI ! where you download it?

[@thethoughtsofmoz5948]

@@ambition112 I just googled it wow looks handy as

[@NorthernChev]

Your car will only use as much octane as it needs. Nothing more. BUT, even if you car requires a premium fuel, it will still, most likely, drive on regular, albeit at diminished efficiency and higher wear. It is NEVER recommended driving a car that requires premium to be driven regularly on anything but premium, despite it's clear ability to do so. On the other hand, if your manual says your car only requires low octane, then there's nothing to be gained by buying premium.

[@jamesg8246]

​​@@NorthernChevThat's not accurate entirely. My car is designed to run on 87 but has audible pinging under certain load conditions on 87 which lead to premature wear. Using 89 or higher and the engine runs much better. Honestly, the average person would never even hear the things I hear because a car is "just a car" and it "makes noises". Those of us who understand how these things work and actually pay attention know better. Preventing premature wear is absolutely a benefit.

[@NorthernChev]

@@jamesg8246 I had to go back and read my comment a couple times after reading your reply... And the only thing I can figure is that you didn't actually read my comment. Because you go into great detail REPEATING exactly what I said...

[@billkallas1762]

Talking about Avgas and showing Jets, is pretty funny.

[@YouTubeviolatesmy1stamendment]

For those of you who still don't get it Avgas is used in piston aircraft not jet or turbine engine power aircraft

[@Fadamor]

Additionally, Simon said it was used mainly in "recreational aircraft". Pilots refer to the planes that use 100LL as "General Aviation" or "GA" for short..

[@TrevorSachko]

@@KZbinviolatesmy1stamendment Many AVTUR engines will run on AVGAS....

[@skyhawk_4526]

At least this seems to have been clarified later in the video.

[@Gofr5]

Definitely don't want to be mixing up your avgas and jet-a or b fuels. It wouldn't be a good day.

[@justandy333]

I remember on Top Gear, Clarkson took a look at the Lada Riva and said "it ran on petrol with an octane rating of 76, That's not really petrol, That's Spicy water!" 🤣🤣🤣

[@randalmayeux8880]

I remember as a kid in the 60s, when my dad would pull into a service station the attendant would come up to the window and ask " fill ' er up with ethyl?" I remember getting into an argument with my cousin over octane. He kept insisting that the higher the octane, the more volitile it was, while I insisted that opposite was true. We were all car nuts, so we combed through Motor Trend, Hot Rod, Road and Track, and other assorted car magazines until I finally got proof that I was right.

[@wally7856]

That gets you into a catch 22 for small engines. The lower octane fuel is more volatile so easier to start for cold small engines (chainsaw/snowblower/lawn mower) but also has ethanol added to it which attracts water and since small engines can sit for long periods of time unused, it can damage them. High octane fuel at the pump has little to no ethanol but makes the engines harder to start when cold due to that lower volatility. Just can't win.

[@nunyabidness674]

Laymans terms, the higher the octane the more it can be squeezed before it goes bang on its own. If a car has a sticker saying "Premium Fuel Only" or something like that it means the engine is a higher compression than average (Providing more power). Running lower grade fuel in these cars won't prevent them from operating, they just won't operate anywhere near the advertised performance and you can have ignition issues. Mid grade is typically the optimal fuel for anything that doesn't have the fill me with premium sticker. Running premium in those vehicles doesn't really provide any additional benefit over mid grade, however running regular will provide bare minimums on performance.

[@dragontoothless4351]

Fun fact: The mid-grade is actually just the pump drawing from both the premium and regular fuel tanks. Which is why it's typically cheaper to buy around 8-10 dollars worth of premium and then top up with regular when using mid-grade, than to just fill up on mid-grade.

[@mylt1z28]

@@dragontoothless4351 fun fact, thats a myth. Look at any fuel island and there are 3 caps, 4 if they also have diesel, 5 if they have ethanol free. I use to work at a local co op and we supplied fuel to many of the local gas stations.

[@nunyabidness674]

@@mylt1z28 They had that right... Mid grade is the pump pulling from premium and regular and the mix happens inside the pump. Intersection of highway 11 and Sunnyside Rd, Milton-Freewater, Or. There is a little corner C Store called Wayside Market and Gas... Take a WILD guess who kept the pumps going... 3 caps is Regular, Premium and Diesel. If they have more than that, it means the station has multiple tanks for the same product. Ethanol - Free is a non existant in Oregon as well as a few other states I can think of. If you want non E85, you go buy coleman lantern fuel in 1/2 gallon cans. Now, regarding your "5 cap" statement on "Any fuel island"... Spacial geometry exists... You got 5 caps on that fuel island, you're talking better than 6 pumps. Those are the stations (Like a QT or Pilot) with multiple tanks of the same product. Mom and pop shop with 2 pumps (Both sides count as 4 fueling points on 2 pumps) only really has enough square footage for 3 tanks in the first place. These in ground storage tanks are typically a volume of 7k gallons and they pretty much occupy a bit more area than the awning over the pumps...

[@pohldriver]

Read your owner's manual! For instance, I have a 2018 Silverado with the 5.3L V8. It specifically says DO NOT use anything other than 87 octane. However, if it had the 6.2L, in order to get all 420 horsepower, 93 octane is RECOMMENDED. But since GM, as well as RAM and Ford, realize 93 octane isn't always available, they are equipped with octane sensors to adjust tuning based on the octane. Running 87 will reduce your performance which only really matters when you're towing or racing.

[@jerrykorman7770]

To add confusion, my ‘13 Ford Focus owner manual states to use minimum 87 octane. However, for best performance, a 93 octane fuel should be used. Especially hot weather driving. So I run premium during summer and regular the rest of the year. I have tried 87 during hot stop and go driving with the A/C on, and that 2.0 liter GDI struggled sometimes

[@raceyrache8463]

Your ecu changes the timing of the combustion process to allow different fuels to be used. Older cars with carburettors don’t have this option and must manually tune the engine accordingly.

[@GodsGladiator]

I run a Hemi Ram it says 89 I typically run 87 all I notice is a .2 change in mpg. Not on a track so don’t know if there is a real difference but I don’t notice it when I run ppl.

[@buysncharge]

All post 1996 gas engines are capable of running low octane. Even a hypercar. They may not like it. But they can do it.

[@farncoisbisson7737]

there is no octane sensors it just calculated by the Ecu.. you can have a ethanol content sensor if you are flexfuel.. it constantly adjust vvt timing and other variable depending on knock etc..

[@StephenJohnson-jb7xe]

In Australia we call it petrol as well, we have 4 types of petrol generally available 91,95,98 and a 10% ethanol blend which is sometimes labelled 94. I noticed that the US generally has lower numbers and initially thought that meant they had lower octane fuel but it’s actually a different scale that they use. While watching a movie set in Africa last night I noticed that they also called their fuel petrol, so I guess there are a few if us using the name.

[@raceyrache8463]

We also have E88 now. The V8 Supercars use it for environmental reasons. This is available to the public from certain locations.

[@Vladimir_The_Impaler]

"Super" was the best petrol ever created in Australia

[@raceyrache8463]

@@Vladimir_The_Impaler so you watched the video and still come away with leaded is best 🤔. Clearly don’t know how to comprehend what research has been done on the dangers and effects of lead. Also we make better fuels that are NOT CARCINOGENIC

[@Vladimir_The_Impaler]

@@raceyrache8463 It was the most wallet friendly fuel, instead of taking leaded hence "Super" off the market, maybe adding a exhaust bag and filter to exhaust system would have helped tremendously to the environment

[@Vladimir_The_Impaler]

@@raceyrache8463 You just simply lack innovation and imagination. People like you always wanna knock-down the wheel of economic efficiency and production, but all is needed is slight improvements.

[@evanr.2586]

Nice that you discussed AVGAS. It is worth mentioning that ethanol cannot be used as an octane booster for airplanes. It is hydrophilic (i.e., is attracted to water) and water in the fuel can be fatal in piston engine airplanes. Water contaminated fuel causes multiple fatal plane crashes every year.

[@thevictim2072]

You are incorrect about your information on ethanol in av gas. It has nothing to do with water. The problems are vapor lock and corrosion caused by ethanol.

[@scooby45247]

As a 93 car driver, i do miss the affordable fill up of 87..

[@A1FAHx]

I carry a blindfold with me every time I push that 93 😉

[@haredr6511]

I carry a Joe Biden, “I did that,” sticker

[@nomadMik]

​@@haredr6511​ I'm not a Biden fan, but those stickers depress me, because they show how pathetically gullible so many voters are. Do you seriously believe Biden has any real influence over OPEC? Or over the Federal Reserve? Or over how basic supply and demand work?? Did whatever school you went to really not cover basic civics and economics? No wonder Republicans fall over themselves to gut education funding, if it results in so many people clueless enough to buy plainly stupid lines like that! And no wonder so many of their voters snivel so much about feeling oppressed, as if being told they're wrong is some kind of affront to their free speech! I'm not ashamed that I'm American, but I'm ashamed you are!

[@walterengler5709]

I played that one section over and over. So two engineers discovered Ethanol could do wonders with controlling knock. But Ethanol could not be patented. So they came up with something that could ($$$). And despite having lead and know the dangers, they changed the name to help hide this. And finally even when confronted with people in the factories making it, and despite having overcome a case of lead poisoning, the one person poured it over their hands to show it was safe to keep manufacturing it for another sixty years. Those were two of the most evil people I have ever heard of.

[@oreotookie]

The Simon unleaded video on this is excellent. Wish I could remember what the name of the video.

[@Steven_Edwards]

That Sonofabitch killed millions with cancers and downstream murders from people being insane due to heavy metals in the water table, that lead has to go somewhere when it's burned and it went in to the air, the surfaces, soil, food, everything. Within a decade of lead being removed from fuel it was obvious there was a decline in crime.

[@statementleaver8095]

11:15 Can't blame Thomas when the Government was Detonating Nuclear Devices sending massive amounts of Heat and Radiation at the Ozone 🤷🏻‍♂️🤷🏻‍♂️

[@UncleKennysPlace]

Nooooo! Detonation is knock; it's supersonic combustion. Pre-ignition (a hot spot lighting off the mixture before the spark) can sometimes cause detonation. No such thing as "pre-detonation".

[@petermostyneccleston2884]

As a Gardener I have been using Petrol in the machines all of my life. In about 2001, I noticed a problem with a machine that I had been using for 5 years. The petrol oil mixture was exactly the same, and the Government had not yet gone public with the announcement that the petrol was being changed from RON95, to E10. Over the next 2 years, I had changed the 2 stroke oil, purchased new machines, altered the ratio of the petrol and oil, and tried to adjust the carburettor, but I still had the machines stalling when I was using full throttle. In the end I put Premium petrol, E5, and mixed at 50:1, which was my original mixture, and the machines are working as they were before the change in the formulation of the petrol in the UK. This means that not only has the petrol price gone up, but I have to use the most expensive of the petrol.

[@4BillC]

It's us little guys that's responsibile for all the environmental problems. That why cars have to hit impossible mpg requirements. All while the rich get to fly around in their personal jets or big corporations puking out terrible and toxic emissions! Personally I like E85, and at about 100 octane it's perfect for my Boosted engine. And I still get 20+ mpg and it cheaper.

[@dale116dot7]

I work with natural gas, it has an octane rating of around 125 or so, it’s not a problem to run 15psi boost at stoichiometric (for emissions) all day long.

[@MAGGOT_VOMIT]

Lead additive was mainly used as a valve lubricant in older engines to keep valves from sticking or floating.

[@Thumper68]

Floating valves has nothing to do with a valve sticking and valves just don’t stick that’s what the spring is for. At no time would fuel be in the valve stem area. Oil lubricates the valve train.

[@imtheonevanhalen1557]

It was a combined effect of resisting out of control quick burns in the combustion chamber, and softening the impact of the valves on their seats. Run an old engine on non-leaded, it'll loose compression pretty quick.@@Thumper68

[@Thumper68]

@@imtheonevanhalen1557 my 68 Camaro is matching numbers all original car 115k original miles runs just fine last 45k I’ve drove it or is that not old enough?

[@martyclakson9226]

The lead in fuel coated the valve head and seat- the bits actually in the exhaust flow. It prevents the valve micro welding to the seat at high temp and pressure- leading to wear. It also created a layer on the cylinder walls which helped prevent piston and piston ring wear. The lead meant that softer steels could be used, which are cheaper and easier on the tools used to cut them. Modern engines now use hardened steels to prevent tiny portions of the seat becoming welded to the valve.

[@ulbuilder]

Not quite sure where the rumor started but there is nothing lubricative about lead oxides. Aircraft still use leaded fuel. Lead deposits on valve stems are known to cause valves to stick. The valve stem deposits can also prevent the valve rotators from rotating the valves resulting in uneven wear of the valve and seats causing them to leak. The lead oxides produced in combustion are more like abrasive sand than they are a lubricant. The lead deposits also accumulate on the spark plugs fouling them. Lead was good at only one thing, boosting the octane rating cheaply. It is bad for engines and the environment.

[@starrywizdom]

In some states of the US, instead of having 87 octane as the lowest & 89 octane as the midgrade at the petrol pumps, all the stations have 86 octane & 88 octane petrol. This has annoyed me on road trips -- since my car is supposed to run on petrol no lower than 87 octane, I have to buy the midgrade petrol rather than the lowest grade, so even though it LOOKS like gas prices are LOWER in those states, I actually have to pay MORE. Seems kinds sketchy to me...

[@pirobot668beta]

Fun Fact! The Jefferson/Jeffery Pine, found in Northern California, has sap that is nearly pure n-heptane! So pure, it's has long been used as the 'standard fuel'.

[@timerover4633]

In World War 2, a lot of the aircraft engines were using 87 octane fuel, primarily training aircraft and transports. It does somewhat reduce the horsepower output, but most current piston engine aircraft engines had predecessors that used 87 octane fuel. The problem is getting the FAA to certify the use of the 87 octane mixture of gasoline and alcohol in aircraft engines. There is also a fair amount of information on the use of ethyl alcohol for aircraft power plants in the U.S. Naval Technical Mission to Japan, as the Japanese were using alcohol for their trainer aircraft to preserve their limited amount of higher octane fuel for the combat aircraft.

[@Benson_aka_devils_advocate_88]

This just reminds us that the current price of fuel isn't due to any technical difficulties but rather the fuel industry knowing they can squeeze every last penny out of us because we've no other options. And they will run a conserted effort to gaslight us into thinking otherwise!

[@MrMancreatedgod]

No. Unfortunately the majority of America currently believe it's Biden's fault. 😞

[@KNR90]

And yet every person I know in the oil industry puts premium into every one of their 5 vehicles. When none of them need it. They also think they are poor, so I picked the wrong industry because oil companies hire any dumbass

[@Lockdown335]

100%

[@233kosta]

Governments are also entirely complicit in this scam, let's not forget that.

[@leetimberman8860]

Actually, our high gas prices are because the government in power doesn't want us to use oil. Allow drilling and gas prices would be cut in half. We need the government out of our way.

[@rachelbarrie5359]

My car is a 2009 vitz and can take 95 but prefers 98. I always use 98. As of currently here in Auckland, the price is over $3.00 NZD. So it's not true that people use the cheapest, but most do. I do what's right for the car.

[@franklinwerren7684]

I remember engine knock!!!! 😅 and the conversion problems with corn gas first came out… like fuel pumps failing or failed when I accidentally stuck unlabeled corn gas in my pickup…. It ate the fuel pump and carburetor innards up… they finally made parts that did not have issues when you used corn gas. And I use it today with no issues😅😅😅. Love the different things that you guys produce. 73’s Frank DE N2JYG

[@kevinmacfarland2875]

One benefit of being able to use E85. Less wallet crushing, just gas up more often

[@IrishMike22]

I love when a video elicits comments from around the globe. Its interesting hearing from regular people like me about their part of the world and the problems we all face 😊

[@downtoearth1950]

Here in Australia our heapest petrol is 91 octane, it has no ethanol we do have a 10% ethanol blend available aswell. Our higher octane levels are 95 and 98.. my 2022 Rav4 has an Atkinson cycle engine in it that will not knock so it is the lowest/cheapest that I use. 😊

[@ADPeguero]

Simon Whistler always giving us much more than just a simple answer. I always get a good "shot of brains" whenever I watch his content. Great work crew.

[@NorthernChev]

He has a phenomenal team of researchers, as he no longer does anything behind the scenes, other than now running the company, for over a decade.

[@bmyers7078]

5:00 My late uncle was a mechanic, who used to tell people to occasionally get an “Italian tuneup”. Get the highest octane gas you can afford & drive, at speed, on a highway for hours. It burns off the “sludge” that can build up in some older engines.

[@joshacollins84]

I've worked with a big hard, caring monster like that man before, & it was such a great experience. Once you figure out that they do care about you as well as the job AND that they aren't hollerin' to be mean is great.

[@ronaldlebeck9577]

Although I knew much of the chemistry, the historical part was quite interesting. I remember my dad getting Ethyl at the gas pump for $0.15/gal. You might not have known that ethyl gas had one slightly humorous spin-off, which is a joke title, "Behind the Gas Station" by Who Pumped Ethyl. Back when I had my 1976 Pontiac Firebird Esprit, the 350 8-cylinder engine was rated for 97 octane gasoline and higher. When the higher octane rated gasoline was being phased out, I had to buy cans of 103+ Octane Gas Booster and put one can full in each 20+ gallon tank of gas to keep the engine running well. That Firebird was one of the last muscle cars and I haven't found any car produced today that was as solidly built as it was. It was one of the few 2-door cars that had the same side impact resistance of a 4-door, due to how heavy and solidly built the doors were. The whole car was heavy and sat low to the ground and handled curves a heck of a lot better than the 1991 Honda Civic I had years later. I miss my Firebird, it was the best car I ever owned and I made numerous long-distance trips in it (I was in the Navy, so drove it through most of the lower 48 back in the 1970s-1980s).

[@ostlandr]

My Brother-in-Law had a Ford Torino back in those days. He knew a guy at the airport, so he ran it on half pump gas and half avgas, otherwise it was unhappy. But sometimes his wallet forced him to run straight pump gas, and he "just let it be unhappy."

[@caylaleon4790]

I love this channel but 5 minutes in I'm already lost 😂

[@ozymandiasultor9480]

Try understanding how differential works, it is even more...ahm...interesting...

[@Arycke]

Also, for octane ratings < 80, a different procedure is used under ASTM D2699 and D2700, called bracketing by dynamic falling level or equilibrium falling level (and octane number is calculated via an interpolation between 2 reference fuels)

[@spidos1000]

Bracketing is done at any octane. Depends on how your engine is set up. I worked in a refinery that did bracketing only and where I work now we do the compression method for 80 to 100 and bracketing below and above those octanes.

[@Bushy556]

It’s not a different method. Just a different procedure under those methods. Did all of that including D909 and D2885 at the refinery where I work.

[@davekirk100]

My dad was one of the first in the UK to own the 'new' Austin Maxi, terrible car, complete rustbucket, but that was designed to run on '5-star' 101 octane fuel. Became to be almost unavailable in the late 1970s, only one fuel station within about 20 miles sold it

[@seanprice7645]

higher octane = higher knock resistance. essentially, it's harder to ignite.

[@TadashiAbashi]

The red 'un makes me trukk mo' zoomie!

[@matthewrappold1459]

It makes da walk-in fassta!

[@PacesIII]

​@@matthewrappold1459 Da walk-in fasta is from da lights in da shoes.

[@phforNZ]

Wot u gitz on 'bout?

[@alexmcd378]

Red trukk go fasta!

[@i-love-comountains3850]

😮That tax free diesel hits different😏

[@marsgal42]

I'm familiar with blue 100LL avgas out at the airport. The acetone/paint thinner smell is distinctive. It's much stabler than car gas and can sit in a plane for months with no ill effects. It costs more than car gas too... In the past they made other grades with different colours: red, green, purple. I've never seen any of them in real life.

[@AnnaAnna-uc2ff]

I learned about this in junior high, late 60s.

[@billwylde4846]

87 octane or 88 octane (Not the E15 variant unless your car can take the 15% ethonal content in its fuel lines), will be fine for your vehicle that mentions about 87 octane or higher. Also, always run the recommended fuel for your vehicle as much as possible as well. You know, the vehicles that recommends 91 octane or higher (Premium) for example. You will get better performance and fuel economy using the recommended fuel compared to cheaping out and filling up with the minimum requirement octane. Read your owner's manual. It will save you alot of headaches and use Top Tier labeled fuel.

[@deadwaterblacksmithing]

Moral of this story, run 93 in your forced induction engines to get more timing advance and more power output. This will also increase fuel economy because more power means less fuel needed to accelerate or maintain a set speed under all load conditions. The part that was missed is that ethanol is very inefficient as its power density is much lower than pump 93. As in the required fuel density mixture for ethanol is 9.7 parts air to 1 part ethanol versus 14.7 parts air to 1 part gasoline. The extra fuel load required drops your fuel economy by roughly 15 to 27% depending on the engine design. Ethanol is also more caustic for the modern plastics in your fuel system and will break them down and destroy your fuel system exceptionally more quickly than standard gasoline so unless your vehicle is designed with higher grade plastics that can withstand the use of high ethanol content fuel then you should not use it. Also due to it needing more fuel per cycle your injectors and fuel pump may be too undersized to keep your air fuel ratio correct causing lean mixture detonation and destroying your engine in grenaded cylinder fashion. Just some added things to keep in mind.

[@NXT_LVL]

Unless youre using E85 in your boosted application then that 91/93 fuel table get tossed... even though E85 burns "cooler" one might say, you need 1.5 to 2x the fuel which is why people tune in LAMBDA over AFR... though in a 700-1500hp boosted application youre not really concerned with MPG, hence for the Drag and Drive events, they have a street tune to run on pump 91. Now for your average turbo commuter it depends most will say 91 though 87 or 89 will work because it has a flex fuel sensor that automatically adjust timing per the octane in the fuel. where in some case E85 is actually 74-78% rather than 85%

[@psychosis7325]

Thats a giant mixed bag of wrong... Ethanol is not caustic, it absorbs water and is quite corrosive to some metals. Also damages some plastics and rubber, generally its the rubber O-rings on things like injectors that need swapping out more so than plastics for running E85... E85 is stoich around 9.8 not ethanol that closer to 9 and you want to be clear about which mixture you're reffing to with high ethanol, I think E85 but I'm assuming many will think E10 especially given E85 likely won't even start. As for timing just going and adding timing does not instantly give more power and economy, its called timing for a reason and is so much more than just more timing = more peak pressure and power, also power does not instantly translate to economy... Even the blanket run 93 worries me a bit. Need to run 95+ RON in most boosted cars in Australia, can't really buy 93 easily here but if you're going to be talking octane and mixtures and stuff and giving advice to people on a global platform you want to add if you're using the Anti Knock Index, Research Octane Number or Motor Octane Number...

[@MrEnjoivolcom1]

Comment needs to be pinned 📌, Simon & guys!

[@deadwaterblacksmithing]

@psychosis7325 we dont have the fuel options the aussies have. Ive seen e85 turn plastics in a fuel tank into wet noodles. If you call thay corrosive then ok, but when it "melts" shit, I treat it like other shit that melts shit. You cant add more timing if your fuel cant take it but in general, more advance is going to give you more power. This post wasnt written for people to go tune their haltec with. It was a generalized post to point out some shit that was missed cunt. Pump 93 nets me around 23mpg in my stand alone tune with 750cc injectors if im not finding the floor constantly. E85 gets me about 15mpg. If i toss in some 400cc injectors from the shelf, pump 93 stays roughly the same after I adjust the tune for nearly halving the injector size, but e85 wont have enough injector for the fueling needed. Seems a bit less power density, and less efficient but more stable is rhe correct was to define ethanol as a fuel. Corn is for eating and coming out the same as it went in around here. Also, im not building a 2500hp drag car or it would be a methanol setup because why not at that point.

[@Aztesticals]

My man your math may be decent but it doesn't always work that way in practice. I get 20.mpg on 87. I get 22.3 on 93. That's not enough to cover the cost difference

[@lazy_lefty]

You forgot to mention E85 gasoline made with ethanol from corn. I live in iowa and ethanol production has been a huge money maker for farmers that were previously struggling to sell excess corn inventory on the food market.

[@LAHSS1940]

We also have E85 in Australia, it’s octane rating is 107… Is it the same in the US🇺🇸?? I have a 4cyl AMG tuned for it and I absolutely love it…

[@gold3084]

LPG (Autogas) has an octane rating above 100, while standard unleaded petrol has an octane level of 91. LPG does have a higher octane rating than petrol though its less energy dense.

[@zublacus]

Correct. The ingredients to increase octane are less energetic than the fuel itself. The performance increase comes from the engine and the optimization of the explosion, not the ingredients in the fuel.

[@sidecarbod1441]

4:12 The two values are not generally combined, the number stated on UK pumps is the RON number, as far as I'm aware only in the US the two figures are sometimes averaged out (added together and divided by 2), this is then known as the Pump Octane Number, PON). The MON number is lower than the RON number because the test engine is run under harder conditions, a higher RPM and with a higher inlet charge temperature.

[@rgbaal]

That is correct outside the USA it will be one or the other and it will be stated on the pump

[@Arycke]

At really low octane numbers and particular fuels, the RON and MON can get really close. I.e. a particular naphtha could have a RON of 45 and a MON of 44 An alkylate could have a RON of 93 and MON of 92.

[@Arycke]

Also, in practice and in research, it is really not commonplace to call (R+M)/2 as "PON." Just bringing this up from my anecdotal experience in laboratory colloquialisms. Typically, it would be referred to as just " R plus M" or "AKI" , so as to avoid any confusion or mishearing of PON for MON for RON when speaking about them, especially if you are running the engines (they are very loud).

[@sidecarbod1441]

@@Arycke I agree PON is just a US pump thing, it is not something that a fuel lab would use.

[@mikefochtman7164]

Here in the US, we often see the notation "R+M/2" (actually they show a vinculum that mathematically is different than the '/' symbol, but lets not go into that here). This is to show the octane rating is the average of 'R'esearch and 'M'otor testing method. It's my understand that in addition to the 'calibrated engine' you discuss, we also use a laboratory chemical analysis and average the results.

[@okaro6595]

In Europe only the RON is used so the values are about 5 octanes higher than in the US. Here options are 95E10 and 98E5. In the past when lead was used the options were 92 and 99 and their mixture which w s marked 95/96.

[@Arycke]

RON and MON are determined by ASTM D2699 and D2700 respectively. ASTM D4814 X1.4 gives the calculation of (R + M)/2 as the AKI Anti-Knock Index, or Octane Number colloquially.

[@Logarithm906]

don't buy a higher octane than you need. Not only does it not improve performance but it may also get you less mileage. It happened to my old motorcycle (carbed). I bought higher octane fuel to test the theory that it'd give better mileage, it actually got quite a bit worse.

[@andrewsmith2591]

I love your monologues, Simon. Your delivery is so funny and entertaining. I know there are a few cuts and edits but, do you ever breathe?

[@BigMobe]

Generally the higher the compression ratio and size of an engine the more efficient it is but also the more expensive as well.

[@BigMobe]

@@aluisious I've worked on diesel, gasoline, gas turbine compressor, and small engines. What you are saying makes no sense at all or trains and aircraft would be using scaled-up lawnmower engines. The larger an engine is the better it is at extracting more power from the same amount of fuel as a smaller engine. As something increases with volume/mass its surface area does so at a smaller proportion. That means less energy is lost to entropy in larger engines. That is part of why there is so much of a push to move outdoor power equipment and the automotive industry over to electric. The rest is politics.

[@TrineDaely]

These days another thing that makes a difference (at least in US) is top tier gas vs cheaper blends. The octane is the same, but I have a direct injection engine, and if I use the gas that isn't top tier (has to do with detergents in the fuel mix, pump will be marked as "top tier") I get nasty carbon build up that really impacts performance and can be costly to have cleaned out. Direct injection is an improved version of the fuel injector, and because it's more exact you really want to be sure to check the manual and see what fuel is recommended.

[@jesses1589]

Newer DI engines are using old fashioned port injection once again to clean intake valves. If it weren't for the emissions system we wouldn't have to worry about that build up anyway. For example, my 19' Camry hybrid atkinson cycle engine uses DI and Port injection or a combination between the 2 whenever needed.

[@dallynsr]

I would call direct injection in a gasoline combustion engine, an improvement to the injector. It does improve potential performance and offer some other efficiency options, but, the carbon buildup issues that they present are remedied by old-school injector systems. Fact.

[@CowboyCree63]

Most General Aviation aircraft actually have quite low compression ratios, often 6.5:1-8:1, while most vehicles are 8:1-10:1, except for diesels, which average 16:1-22:1

[@roycesmith9182]

He is mistaken about aircraft engines being high compression,you are correct !

[@davidlloyd3116]

I drive a 1275cc MG Midget (1974). I need at least an Octane number of 95, due to the high (8.8:1) compression ratio. I also add an octane booster to improve the octane level. I live in the U.K. and octane values around the 80s aren’t available, and ethanol in the fuel corrodes the pipework, and often separates over winter storage.

[@GalaxyFur]

In the UK, you are ripped off in the gasoline market. Most vehicles around the world today are designed around an 87 octane gasoline. (87 octane in Canada and the U.S. = 91 octane in Europe) Yet the UK is basically the only country around that doesn't sell 91 octane as its base fuel for most vehicles. So, you start off by paying mid-grade prices for the cheapest fuel offering from the get-go. Be careful when it comes to octane boosters, too, as most of them are ineffective and often even reduce octane in gasoline. Most octane boosters are certified scams. Also, many octane boosters will tell you they raise octane by 7 points or 6 points. What they don't tell you is that it takes 10 points to raise your octane level by 1 single octane number. And most bottles only treat up to 15 gallons on top of that. However, most octane boosters don't post the points because they don't raise the octane at all. The best way and only way to effectively improve octane is by buying a higher grade of gas most experts will tell you.

[@davidlloyd3116]

@@GalaxyFur Thanks, most interesting. I am always concerned about which fuel to use in my 50 year old car!

[@zacharystevens7801]

Here in Australia 91 is our lowest octane, 95 and 98 are normal performance fuels found in every fuel station 104 and 109 high performance fuels are sold in few but somewhat common fuel stations (ethanol)

[@Shabass]

In australia you use RON to calculate octane. Us and canada use aki rating. So even if your's numbers is higher, ordinary fuel is about the same in preingnition protection.

[@wich1]

Exactly, North America and Europe+Oceania of course use different systems, because why would we use the same one. And being a European, the one we use is of course the better one 😝

[@Bob-qk2zg]

Petroleum was originally an illumination industry. Crude oil was simply distilled to get kerosene which was sold as a cheaper substitute for whale oil to fuel lamps. Gasoline was an unwanted byproduct having no use until Henry Ford came along.

[@mitchalwaggoner1648]

Thabk you for including Paul's commentary on GA side.

[@magnemoe1]

Just to point out its just small planes with piston engines who uses the leaded gasoline. Jet engines uses jet fuel who is basically refined kerosene. Also modern cars tend to adjust to avoid knock but if you have an car with high compression its better to use higher octane fuel.

[@okaro6595]

There are also diesel engine planes that use jet fuel or normal automotive diesel.

[@TheChrisLeone]

I've gotten into basic tuning of my car, I was very intrigued by power gains with little work. Tuning for 93 adds a significant power bump, but only if tuned properly

[@negativeindustrial]

Sports cars are tuned for 93/98 from the factory. Modern ones use complex systems to allow power based on available knock resistance on the fly.

[@ostlandr]

Trying to remember which vehicle I had- was supposed to be fine on 89, but unless you ran 91 you would get knock on engine load at low RPM and the knock sensor would correct the timing. On long trips over hilly interstates, I'd run 93. The power boost kept it from hunting in and out of overdrive as much. Got better mileage, but not quite enough to make up for the difference in fuel cost.

[@dragontoothless4351]

Fun fact: Though the editor put jet aircraft clips in while Simon was discussing 100 Low Lead (100LL) AVGas, those jets run on JetA High grade Kerosene, not gasoline. 100LL is really just used by small prop planes such as the Piper Seminole and Cessna 152. And as someone who got splash back in my face while refueling my Cessna 172 once (the result of a gust of wind while I was fueling which pushed me and thus the nozzle, and sent the blue-dyed fuel back at me), I can vouch that gasoline is extremely bitter in taste (I spat out as much as I could). If you were wondering, the blue dye is added both to help find potential leaks, and more importantly, as a means of ensuring there is no cross-contamination of the fuel for 80 and 100LL aircraft. Each of the three types of aviation Fuel (80, 100LL, and JetA) are color coded, with 80 being red, 100LL being blue, and JetA kerosene being clear. If you were to add either of the other two types of fuel to your tank, the dye reacts much like bleach to food coloring, in that the fuel turns clear, and so makes it appear during the preflight fuel sampling check (which is what is shown in one of the photos) as if you have JetA in your tanks which would do serious harm to a gasoline aviation engine.

[@ACME_Kinetics]

To add, piston aircraft engines are generally significantly lower compression than modern automotive engines and would typically run fine on 87. However at higher altitudes (lower air pressure) a high volatility fuel can experience localized boiling under certain conditions. Essentially "vapor lock" for those old enough to remember that term. So 100LL it is, for now.

[@raceyrache8463]

The colours are added also to identify each fuel.

[@JD-ft5zq]

They do the same idea with diesel, on road is green, if road is pink. Which years ago was for sulfur content. Now there's little difference because of environmental standards

[@TheHannukahZombie]

@@ACME_Kineticsno, GA aircraft engines would not run just fine on 87. Stop talking, you have no clue what you’re saying.

[@raymondmartin6737]

With regular octance gasoline my 1982 Pontiac Trans Am with an earlier fuel throttle body fuel injection which did sometimes knock and I had to use higher octane gas to avoid the knock. I am glad that I only owned it for two years and 50,000 miles on it, with other problems such as a leaking manifold, camshaft wear, a rattling hatch back and paint that would not stay shiny, when repolished. I traded it in in 1984 for a Monte Carlo SS coupe. which developed a fan clutch problem, high energy ignition had to be replaced, a water pump broke at 30, 000 miles, and a right side electric window being stuck closed. Also the carburetor had to heat up to be driven. I sold it privately at 37,000 miles. While these are some other auto problems than just Octane, I think autos perform better with less defects now. 😊

[@jesses1589]

I use to be a GM driver until I bought my first Toy... Not going back.

[@ursanbear]

I'm still trying to figure out how $0.05-$0.10/US gallon worth of chemical increases that gallon $0.90 from 88 to 92-93 octane.

[@rgbaal]

Because that is what people will pay.

[@danielsantiagourtado3430]

Love these videos fact boy! Keep going!🎉🎉🎉🎉❤❤❤

[@jamesturner2126]

2:55 The Crankshaft Position Sensor and knock sensors sense the irregular combustion, they provide feedback to the computer. On a V8, it takes 1/4 of the crank trigger wheel to pass by the crank sensor to monitor the performance of 1 cylinder. If that 1/4 of the wheel moves by too quickly, obviously that cylinder produced too much pressure from irregular combustion. The computer will THEN listen to the signal from the knock sensor, to determine the intensity of the knock on that cylinder it identified, more knock more voltage from the sensor. From there, the engine computer can take actions against that flawed single cylinder or all the working cylinders of the engine, depending on the situation. FROM THERE, the computer is programmed to give you the best performance it can without blowing up your engine. You will almost never hear a ping in a street legal car, not 1 with a computer. These calculations happen THOUSANDS OF TIMES faster than our brains.

[@i-love-comountains3850]

That's fascinating are you an automotive engineer?

[@jamesturner2126]

@@i-love-comountains3850 I studied automotive technology. Elon Musk hired me as a technician, Elon assigned me to be a fabricator, and then Elon fired me. Now, my hobbies include welding together custom lithium ion battery packs. I'm boring.

[@JD-ft5zq]

I'm a bit confused you mention a V8 engine, but also stated the harmonic balancer making 1/4 of a revolution per cylinder? Ummm no. That would be 1/8 if it's a V8 engine. 1 full revolution of the balancer means every cylinder went up and down once. While yes only 4 of those produced a power stroke in that 1 revolution.

[@JD-ft5zq]

You also imply that A CPS, crank position sensor, monitors the entire rotation of the harmonic balancer. It does not, it's not a cogged wheel like your ABS uses. It is far more basic and signals roughly TDC on cylinder 1. Or for this of you old enough the notch that you'd view with a timing light back in the day. The computer then uses a couple to dozens of other sensors to constantly make five adjustments within the range the PROM will allow

[@jimmyjimjims7483]

They started putting stickers on the pump where I live in Texas that says "not for use in vehicles manufactured before 2001" and I noticed issues in my 91 Toyota before they put the warning, it would stutter and idle weird up until I changed octane ratings.

[@hhjones9393]

Good stuff Simon! I liked not only the content but also you nailed the delivery.

[@CrankyQuokka]

When you mentioned the creator of Ethyl lead I immediately thought I'd have to suggest a Bio story about him due to the rest of his environmental impacts and demise. Glad it was added at the end. Another great episode 🙂

[@pohldriver]

There was a whole episode devoted to him. I believe that was on Biographics, though, thus no cross promotion anymore.

[@MnementhBronze]

​@@pohldriveranymore? Did he stop doing biopgrahics?

[@lukeb6771]

⁠Simon’s/TIFO channels have been going through some content reorganization over the past few months (he made a brief video on it on either bio or geo, I can’t remember.) Because of the sheer amount of content they release, they’re honing in on which specific channel each subject should be posted to. I think they may even be creating new channels. Biographics is still very much alive.

[@hookedentertainment9089]

As a new owner of a 2 stroke outboard and a long time whistler fan this videos timing is uncanny

[@noneshere]

2 stroke engines are the best engines ever made. They have few parts and glactic rpms. I remember suzuki T500 2 stroke street bikes. They didn't need a turbo. Sadly US government has banned 2 strokes because 4 strokes are slower, heavier, and more parts are sold to repair them ; thus government makes more tax revenue

[@JD-ft5zq]

​@@noneshereyeah that's no where near the reason. Did you ever wonder what happens to all the oil mixed in the fuel? Government banned 2 stroke personal water craft(jet skiis) around 2006. It got to the point there was so much oil in the water your boat hull would be a yellowish color after a few days in the water. The air is no different, but yeah it because 4 strokes cost more?

[@roycesmith9182]

2 stroke with castrol r 40 best smell in the world

[@richdouglas2311]

I own two cars with the same 4-cyl turbo engine. They get 215 mph on 87 octane, but can use up to 93 (where they realize 255 mph). Where I live, you can get only octane, but I've found a particular fuel additive that clearly raises that--I get faster acceleration if I put this rocket fuel into the tank. 6 ounces raises the octane level of my 13 gal tank by two points.

[@Iowa599]

Lead is also a very good lubricant, so LL100 is also great for 2-smokers (like snomobiles).

[@worldfinder7996]

Always answering my questions

[@jeffdriver3000]

I own a 1968 Mustang with the original 289 engine. Back when the car was manufactured regular gas had an octane of around 91 and Premium was around 97 octane so I run premium in it now

[@TrineDaely]

You having to put a lead replacer in it, too, or has a work-around been found for that?

[@raceyrache8463]

@@TrineDaelystainless steel valves and seats. Lead was also a lubricant for cast iron engines.

[@raceyrache8463]

Nothing a quick turn of the distributor can’t fix. You would’ve needed to advance the timing to smooth your engine out. If went with a different cut camshaft you can get more power from the same fuel.

[@Vladimir_The_Impaler]

Leaded is the is the best

[@raceyrache8463]

@@Vladimir_The_Impaler and illegal and carcinogenic. You mean cheap and nasty

[@richardmarsh1332]

As guy born in the 1950s and driving cars back then we had a choice of Regular/ Super/ Super plus leaded fuel. These were 91/99/ 101 octane. Having worked on a number of engines over the years you got used to reading the colour of the spark plugs. When unleaded fuel came in all that changed because it did not suit many engines that were really looking for 99 octane and many needed their ignitions retarding to avoid "pinking". These early unleaded fuels generated high levels of soot/carbon and played havoc with older engines. Eventually super unleaded was available and the quality of fuel started to impove. Whilst techically it could be argued you dont need to use super unleaded in the average car, over the years of reading the colour of spark plugs you will always find using super unleaded results in a cleaner burn (less soot build up). In my opinion using super unleaded keeps the soot levels down, reduces carbon build up, keeps your oil cleaner, and less chance of clogging up your cat. I know it cost more money but in my opinion its worth it. I always use Tescos "Momentum" as this is 99 octain.

[@tyrannicpuppy]

I love these seemingly random topics that just tickle the brain in the best way. Learning something that will most likely be of literally no use in modern life but is still fascinating nonetheless. Also, I find it thoroughly entertaining how casually ok with horrible deaths for bad people Simon has become since starting the Casual Criminalist. The whole 'oh no' bit about the guy who made all these things just rang with the same energy as the whole 'Execute Him' howls on CC.

[@ThomasNeal]

You should do a video on why most gas pumps became self-serve

[@jonlyons1033]

As a petroleum distilate distributon technician for a multi national corporation, I can assure you that it is about saving you both time and money, time spent in the store dealing with a min wage mouth breather and money by avoiding that special offer on two bags of stale doritos. Nothing to do with board members trying to automate out said mouth breather. No. Nope. Not at all. In case you're wondering, yes. I am the mouth breather.

[@ThomasNeal]

@@jonlyons1033 well yeah that’s why I said “most” I was hoping he’d include why some states still don’t allow you to pump your own gas

[@jonlyons1033]

@ThomasNeal I wouldn't know. I'm in nz. I imagine it's something to do with the litigious nature of cretins who have accidents then sue others for not accommodating their own idiocy? Just a hunch.

[@domhamai]

In the UK our options are 95 or 97, maybe 97 won’t make much difference in its own, however recently all 95 has become 10% ethanol whereas the 97 remains 5% ethanol, therefore buying 97 means you’re getting more pure petrol and will see better mileage.

[@CalculatedRiskAK]

In Europe, octane ratings given are generally the RON, while North America uses the (R+M)/2 calculation (also referred to as AKI). In short, octane numbers in North America are around 5-6 lower than most other places in the world, despite having the same resistance to knock. You'll see normally between 92 RON and 98 RON in North America.

[@kampar82]

And the 5% is more stable in storage, which is a consideration for some people.

[@PatrikKron]

Most cars are safe to use with E10 (95), but some have increased wear, so for certain models 98 is what the manufacture recommends. Those cars could previously run well on 95 when it still was E5.

[@Pugjamin]

Up to 10% - however quite a few people have tested and found that most “e10” is still between 0 and 5%

[@Gofr5]

Depends where you live. In Ontario Canada, between all 3 grades of fuel, you have to have 15% ethanol combined. As a result, most places just have 87 at 10%, 89 at 5%, and 91 at 0% to get that combined 15%. However some brands do have a flat 10-15% ethanol blend across all ratings and don't offer any ethanol free option as a result (looking at you Esso). It's fine if you are just putting in 87 as you'll get the ethanol regardless of where you fill, however I like to try and stick to pure gas for my motorcycle, which does take 91. As such I only fill it up at certain brands that I know have ethanol free 91 (Shell or Canadian Tire usually).

[@Arycke]

MTBE is added to some gasoline in Mexico up to about 14% by volume.

[@travisolander4749]

Just an FYI: Most modern cars (2015+) have much higher compression ratios (11:1) than older motors (10:1 or even 9.5:1). Most engines with a compression ratio above 10.5:1 will benefit long-term from 91+ octane.

[@MikeDQB]

I've tried explaining this to people so many times and they just don't get it. Maybe I'll just link them to this video ... well ... they still won't get it [because they choose not to] but hey you'll get another view ... maybe. LOL

[@Charles-js3ri]

Me too!

[@stanettiels7367]

I bet you two are a barrel of laughs at parties 👍🏻😂.

[@PacesIII]

The easiest explanation is the average car uses the cheapest gas.

[@gpaull2]

@@stanettiels7367- Based on comments I’d prefer to talk to them over you.

[@MikeDQB]

@@PaperRaines yeah I’ve tried to explain that if your car calls for it you need it otherwise it’s a waste. People argue that they can “tell the difference” and I just let it go.

[@silentracer911]

Octane is the resistance to combustion. The higher the rating the more resistant it is. You want it to ignite when the computer says, not before or after

[@Thumper68]

Lol octane been around way before computers were in cars.

[@ricktaylor3748]

Higher octane is the resistance to "spark knock." High octane gas is more efficient than low octane gas, it burns slower and cooler. Ethanol attracts moister, that's why it's less efficient, and not good for your engine. Ethanol laced fuel destroys small or 2 stroke engines. It's good to run Lucas octane booster.

[@74mayberry]

One thing about the aircraft segment, the gasoline used in aviation is for small, private single/dual engine aircraft. The video shows a commercial jet aircraft which all us “jet-a” fuel, which is very high grade kerosene.

[@mac24seven]

For what its worth... In Nicaragua, putting "Super" in my car nets me higher mileage than regular. It shouldn't be that way in my base model 2007 civic, yet that's the way it is. I think we have lower quality gas here...

[@stephenschroeder6567]

Excellent presentation Simon - thank you to you and your crew. I especially liked the history portion and the people mentioned. The aviation gas portion was very interesting.

[@Brandon_Makes_Stuff]

Moral of the story: Run the Octane that the manufacturer recommends for your vehicle. Higher octane than recommended results in power loss and worse mpg. Your engine ain't fancy enough to burn it properly. Too low octane and you suffer terrible performance and risk damaging your engine cuz the fuel blows up before it's supposed to. Your fancy engine needs the expensive stuff.

[@Thumper68]

BS you can run higher octane or premium fuel in anything that only requires regular and get the same power and mpg only thing your losing is money. And nowadays they have knock sensors and you can just run regular in everything bans save money.

[@Brandon_Makes_Stuff]

@@Thumper68 Wrong. You can do it on vehicles that specifically state you can do it, but even most modern vehicles won't adjust for it. I literally just wrote a research paper on this.

[@Thumper68]

@@Brandon_Makes_Stuff ok whatever you say. I guess your research paper defeats my dads 50 years as master mechanic and machinist and experience and my 30 years experience learning from him. Building race engines etc. And knock sensors have been in cars along time 40 years and since early 2000s you probably can’t find a vehicle without knock sensors and there exact purpose is to tell the ecu to change timing to stop it. You better hope whoever is grading your research paper doesn’t know anything about engines.

[@Brandon_Makes_Stuff]

@@Thumper68 Yup, you're still wrong. I've built race engines too. You can literally activate your knock sensor and shut off your engine by using the wrong octane. Just because your vehicle has a knock sensor doesn't mean it has variable timing. And just because your vehicle has variable timing doesn't mean it will automatically adjust to optimize it's efficiency with different octanes. Like I said, run the octane suggested by the manufacturer. And even like the video you apparently didn't watch says, lower octane fuel is actually more energetic. You should read my paper, you might learn something.

[@Thumper68]

@@Brandon_Makes_Stuff I know exactly how octane works. And the entire point of the knock sensor is to tell the engine to change timing but the difference between 87-91 is not that big of a difference. Not like going from 87 to pure methanol like we ran in our 700hp sbc 30 years ago lol.

[@jamesdellaneve9005]

It's more than just knocking. A slow steady push throughout the stroke cycle gives you more horsepower. High octane simply stated burns slower. Water injection is the poor man's high octane.

[@bellmattwebb]

Great work. Keep it up team!

[@coldmoonlight6361]

A long time ago, in a galaxy far away.... 93 costed half as much as 87 currently does.

[@ricktaylor3748]

I remember what Amoco and Sunoco Premium was 104 octane, it cost $.35 cents per gallon for Premium, regular was $.27 cents. There wasn't any unleaded gas back then.

[@DanielleWhite]

Being a motorcycle rider I sometimes get models where this wasn't translated well for the US market and it's listed in RON only. Around 2000 in the northeast US (at least) there was an awareness campaign that using a higher grade than the vehicle requires is typically a waste of money. The simplified way it was presented led to some people taking it as "no vehicle needs higher grades." At the time I had a sports car and motorcycle that did require it. I got to deal with a number of patrons of the gas stations believing they were being helpful by advising me that I shouldn't use premium grade. These days I have a motorcycle that requires premium and a car that doesn't and every time I pull up to the pump I have to take a moment to make sure I select the correct grade

[@233kosta]

In Europe these days you also get a difference in ethanol content. Some places in France sell "high octane" (it's like 3 points, pish-all difference really) for more or less the same price as regular. The benefits from changes in engine timing are minimal, even on the performance-oriented engine in my bike, but the lower ethanol content (5% by volume, vs 10% for regular) means the fuel itself is a bit more energetic and that translates into an overall saving.

[@a92gsxdsm]

99% of I.C.E. vehicles these days are tuned to run on multiple octane and ethanol ratings. Heck some are even flex fuel. I as a life long tech for many race teams and manufacturers say to stick to what your manufacturer recommends. Your spot on about KNOCK.

[@SegwayBossk]

Got my car tuned for 93 octane only a few years ago when it was very cheap in the US. Now 93 is $4-$5 a gallon but I get mid 20's mpg so it balances out

[@mechntechbeau]

I can get 100 octane from Sunoco right here by my house. My twin turbo 632ci big block loves it. She makes 2650whp and 1859wtq on it, but in 7th gear on the highway she still only gets 6mpgs. Thank God she's got a 25gallon tank.

[@tomholroyd7519]

because you don't care how much it costs (environment, humanity, or simple cost $$)

[@mechntechbeau]

Bracket car I make money off of it

[@dharmachile999]

Selfishness runs deep in the American spirit.

[@seanprice7645]

2650 holy sh*t. can i have a ride lol.

[@Aspartame69]

@@tomholroyd7519 Nor do all the people who have programmed you to type that comment as they fly and sail around the world on private jets and luxury yachts. Contemplate why your main complaint is about the simple pleasures of normal people.

[@Flies2FLL]

For a short time I lived in Mexico with my '85 Porsche 928S2 5 speed, which was a car originally sold at a dealership in Vienna, Austria. It was brought to Flori-Duh in 1985 and "Federalized" by it's first owner, who got it titled in Flori-Duh and then "de-Federalized" it via removing the bullshit electronics that had been installed and the removal of catalytic converters that the car never had from the factory. I lived in Orlando, Florida at the time, and decided to try an experiment: Since the car had no catalytic converters, I took the car to this wonderful town called Orlando, Mexico and went out to the local Orlando Executive Airport and bought five gallons of 100LL, or 100 octane low-lead aviation fuel, which is dyed blue. Doing something like this in the United States is HIGHLY illegal, that I why I did it down there... 100LL doesn't smell like gasoline, more like some sort of solvent. And it is truly a very light blue color; If it is mixed with automotive gasoline, the blue dye instantly dissolves; This is so that airplane pilots can tell if their fuel has been contaminated. Also, 100LL has a distinctive exhaust smell that anyone who flies light airplanes can tell instantly; It doesn't have the disgusting smell that automotive gasoline produces when burned in a non-catalyzed system, the "old school bus" stench. Anyway, since I was in MEXICO...I decided to pour 5 gallons of 100LL Avgas into the tank of my high compression 4.7 liter SOHC V8 powered car, thinking that the 10.4:1 compression big block German V8 would love the stuff....But guess what? It ran no different than when it had my usual Chevron 93 octane fuel. But after about 5 days of driving, it actually started to feel a bit down on power? So on a hunch, I pulled the plugs and they were FOULED. Yes, they had all sorts of deposits, and this from only about 40 miles of driving! The tank had at most 2 gallons of Chevron when I added the Avgas, yet this mixture, which I figured probably brought the tank average octane rating up to around 97 at best...Promptly fouled the plugs! OK. I cleaned them up and reinstalled them, and then promptly went and filled the tank with Chevron 93 octane; The low fuel light was on, something I never let happen, but in this case I wanted to see the results. Thus, even with 10.4:1 compression [no knock sensors...], the 100 octane fuel: 1. Did nothing. The exhaust smelled like the Piper PA-44 Seminoles that I used to instruct in, but it felt no more powerful at all. 2. It fouled the plugs. NOW, that could have been from the small amount of lead in the fuel, but the plugs had fluffy black carbon on them, something I had not seen before; I suspect that octane was the culprit. Here's the thing: Engines are designed to have occasional detonation. This raises temperatures and keeps the plugs and everything else in there somewhat clean. When you add extreme octane, you reduce temperatures and as such you increase the chances of fouled plugs and incomplete combustion. I guess an engine with a knock sensor could take advantage of this extra octane, but these systems are pretty benign about increasing timing but very serious about decreasing it when knock is heard! My recommendation: Use Chevron, and use the octane your car's manufacturer recommends.

[@LearningFast]

In a nutshell. Do exactly what the car’s manual says to do unless you have modified the car’s engine, intake, or exhaust. Once modified you should use the highest Octane available that the car can support.

[@heronimousbrapson863]

The jet aircraft shown in the video don't use avgas, they use a different fuel entirely. You did clarify that later on, however.

[@JonGretarB]

Here in Iceland we exclusively use 98 octane. But in special gas stations we can still get 95 for older cars. (Edit: misremembered this. See comment)

[@kwinvdv]

​@@aluisiousas mentioned in this video, this higher octane (equivalent) rating can also be achieved by mixing in ethanol, which is likely what Iceland is doing. So no complicated refining needed, just an ethanol additive.

[@kwinvdv]

In the Netherlands it is similar, although 95 is a lot more prevalent still.

[@JonGretarB]

@@aluisious yeah I misremembered this. 95 is the standard and 98 available in select places. And it is the 98 that older cars need as we just switched to 95E10 that is 10% ethanol unlike 5% that was the standard before. And older cars from before 2011 do not handle the ethanol rich mixture well.

[@JonGretarB]

@@aluisious but anything lower than 95 has not been available in decades.

[@JonGretarB]

@@kwinvdv yeah. Ethanol mixed.

[@hammersandnails1458]

Due to different measuring methods, (ROD vs MOD) European octane ratings will be higher for the same fuel. EU 95 = US 90, for example.

[@jeffsmith9305]

Airplanes aren't generally high compression on the ground. The issue is that they fly above the ground where the air pressure is lower and their practical compression doesn't go down, making then subject to detonation.

[@philbenson2186]

I literally already know this but for some reason and somehow I actually feel that I've learned something new. Literally listen to your videos every day thank you to you and all your team. More car videos please 🙏 would be the next Jeremy Clarkson or just as popular. Total legend ❤

[@clipsedrag13]

don't EVER mention Jeremy Clarkson in a comparison to anyone

[@philbenson2186]

@@clipsedrag13 ok name a car reviewer that's more famous and successful. It's a compliment. I even said how well known he is in a correction. Love him or hate him his career is unprecedented. Which makes the comment even more valid and saying I prefer listening to this channel more than watching him.

[@andrewkappler5503]

Putting surgar in your gas tank will give you a extra 200 miles

[@FurtiveSkeptical]

Save some for the grueling walk/hitchhike to the nearest phone signal/tow truck/service bay to report your vehicle has died from complications of Diabetes.

[@andrewkappler5503]

​@@FurtiveSkepticallol yes

[@theemmjay5130]

I've heard of engine knock, but automotive history is one of the many, many things that interest me.

[@jaykaufman9782]

In the 1930s, Eddie Rickenbacker, the American "ace of aces" fighter pilot in WWI, convinced Congress, the aviation industry, and the petroleum industry to upgrade American avgas from 110 octane to 140 octane (if I recall the numbers correctly). It was a chicken-and-egg situation: Aviation engine makers weren't going to upgrade to 140 octane when no one was refining such fuel, and refineries weren't going to produce the high-octane blend with no market ready for it. Rickenbacker lobbied everyone concerned for years until Congress appropriated cash for Army Air Corps planes with such engines stipulated, and everyone moved forward at the same time. The rest of the world used lower octane avgas. When WWII broke out, President Roosevelt was anxious to help Britain and the other Allies in whatever way he could. (The scene in "The Darkest Hour" (2017) when Churchill (Gary Oldman) listens in disbelief as FDR explains the U.S. will provide aircraft only by rolling them across the border is total B.S. The filmmakers should be slapped.) Among other measures, Roosevelt ordered the U.S. begin providing the high-octane fuel to the Royal Air Force and Fleet Air Arm. This was a huge secret. The RAF gave their old fuel the cryptonym "Blue" and the new stuff was "Green." (This is what caught my attention watching the video. So *this* is the origin of these code names.) The RAF used only low-octane avgas in the Battle for France. They knew they would have aircraft shot down, and they didn't want the Luftwaffe discovering their secret. But when the Battle of Britain began, they pulled out all the stops and Hurricanes and Spitfires burned high-octane fuel. (Now this video says their performance would be barely effected, but I read this was a real advantage to the RAF in 1940.) The Germans noticed the British aircraft had much better performance over Britain versus how they fought just weeks before over France. They immediately assumed they were facing a more recent, mechanically and aerodynamically improved version of the Spitfire and Hurricane, but this didn't seem to be the case, from studying crashes when air battles continued over France. The Germans weren't stupid and they wondered if Britain had higher octane fuel, the same stuff the Americans were hoarding and refused to export, but RAF Fighter Command had strict rules of engagement by which aircraft with Green fuel broke off action anywhere near occupied France, Belgium, or the Netherlands. Despite this order, at some point a British fighter was shot up over the Channel, and came down over the Continent with enough fuel left in her tanks for Luftwaffe analysts, and the secret was out. Though the UK and US kept up the fiction the US wasn't actively helping the RAF until after Pearl Harbor. Now someone please, please tell me what I got wrong. (And fuck The Darkest Hour!)

[@anousenic]

Well, this video said that performance would be barely affected if your engine is not using high pressure and is basically optimized for low octane. Possibly the planes had to combust the fuel in high pressure and the lower octane resulted in knocking and incomplete burns, wasting potential energy and reducing efficiency. The high octane would have mitigated that, allowing the engines to operate more smoothly and extract (even) more energy from the fuel.

[@christopherkelly577]

My understanding is that performance engines do indeed respond better than lesser quality fuel. I did use diesel BP Ultimate when I had a turbo diesel Saab 93....that had 150 bhp and 220/230 torque standard and it did feel quick and seemed to last longer than regular diesel...was a mechanic who advised me to use it when I could as it helped the DPF/engine in general as it had done 240k/literally the distance to the moon. What a car it was. Paid £480 for it. Class.

[@ACME_Kinetics]

The problem is that octane rating is not a measure of "quality" and has essentially nothing to do with diesel engines at all.

[@noneshere]

Lower octane burns violently & leaves lots of carbon . Higher octane burns cooler & cleaner - a 20 year single piston, double valve, GY6-150 builder & rider .

[@jaymacpherson8167]

At ~2:10 - Gasoline is a couple to a few Hundred hydrocarbons plus additives (far more than dozens). At 12:12, BTEX is implied as a current anti-knock component. BTEX has been in gasoline from the start, and have consistently been the largest fraction of gasolines by volume. Simon, you left out the first replacements for tetraethyl lead…methyl-tert-butyl ether (MTBE) and tert-butyl alcohol (TBA).

[@the_hamrat]

Absolutely correct. For such a week researched piece I think that these are glaring omissions

[@billkallas1762]

People who can't understand octane requirements are pretty "slow". Use what your owner's manual says.

[@lp-xl9ld]

"If you run out of gas, get Ethyl. And if Ethyl runs out, get Mabel!" --Groucho Marx, 1933