Whadayamean Unleaded Fuel Will Trash My Valves?

Now that GAMI's G100UL is fully approved and awaiting distribution, owners are hearing questions about how unleaded fuel might cause valve damage in aircraft engines. It was once a thing in car engines, but in this video, AVweb's Paul Bertorelli examines the issues and finds valve seat recession an unlikely consequence of using unleaded aviation fuel.
Addition AVweb videos on unleaded fuel
The Long, Twisted and Slightly Ridiculous Story of Avgas Part 1
• The Long, Twisted And ...
The Long, Twisted and Slightly Ridiculous Story of Avgas Part 2
• The Long, Twisted and ...
G100UL Approval
• G100UL Approved Now What?

[@cartmanrlsusall]

Unleaded should have been standard 30 years ago

[@redcat9436]

No.

[@austindoud273]

@@redcat9436 you're right 50

[@silasmarner7586]

In planes? Perhaps so. In cars. Yep it already was.

[@ljfinger]

And until a couple of years ago, I thought it was.

[@seanfyodorovich5230]

Agreed-- there is no excuse especially since the lead is spread far and wide from altitude. Particularly as these things are usually the plaything of people with enough money to deal with the engine issues.

[@SimonButler]

Another great presentation. I don't really understand how someone is monotone and so engaging at the same time. Don't ever change.

[@davidoickle1778]

Humour!

[@loddude5706]

@@davidoickle1778 - The captive irony of slingshot lateral thinking? - aka 'inherent cool' : )

[@silasmarner7586]

He has a unique style and micro-inflections (izzat like micro aggressions?) in his voice make it just like you said. It's kinda magic.

[@idkidk8278]

Watch on 2 times speed

[@mrbillgoode]

I think his dentures gives him the kind slurring swag that causes vulva turbulence.

[@needleonthevinyl]

Not installing improved valve seats until 2019, when the push for unleaded fuel has been known to be coming for decades, seems absurdly short-sighted.

[@AwestrikeFearofGods]

Maybe engine-replacement sales was part of their business model.

[@leftcoaster67]

Paul provides no B.S. and a realistic approach to aviation. Thanks Paul!

[@RickBaconsAdventures]

An important point here would be that likely all aviation engines use aluminum cylinder heads, which should all have valve seat inserts, and those inserts may as well have been made from good alloy metal. The cars of the 60s and 70s had cast iron cylinder heads and just used that material as a valve seat. There was no need originally to have inserts at all unlike engines with aluminum cylinder heads

[@ziegle9876]

That was indeed my understanding too. Though I had Alfa Romeo with an Aluminum engine and valve seat recession was a problem...

[@RickBaconsAdventures]

@@ziegle9876 I guess they just didn't use a good enough alloy for the seat inserts?

[@ziegle9876]

@@RickBaconsAdventures Yes, they did not foresee such a radical change in the fuel when designing the engine... Another thing that Paul has not spoken about is the likely addition of cyclic aromatics to achieve the 100/130 rating.... They not only degrade with time, they are also highly carcinogenic (guess why gas stations are all self-service since "unleaded" came about) and not good for many elastomers/plastics (think windshields). The lead content of current 100LL is so low that it is irrelevant, and it makes the fuel long term storable and stable. It is really a pity that we can't have leaded speciality fuels like for aviation, motorracing etc.

[@swell07_]

@@ziegle9876 are you insinuating that leaded fuel being combusted all over is the better solution

[@IstasPumaNevada]

@@ziegle9876 Self-service took hold for the same reason as many changes in retail; because it was more profitable for the owners of the gas station, who could sell more gas more quickly for a given number of employees. You don't need a conspiracy to explain that one.

[@crackleradio]

Nice one, Paul. You mentioned the availability of UL91 in Europe. I've been using UL91 in small, old Continentals (A65-C90) and Lycoming IO320's for many years. Limited experience, but the only difference I've seen is no plug fouling or valve sticking. No difference on the valve seats, and I borescope every 50 hours. Combustion chamber and exhaust port are a lot cleaner. Oh, and it somehow smells a bit less horrible.

[@keefgtp]

You're saying the only difference is that it's better in every way? Dang, it's almost like we should've switched 40+ years ago.

[@michaellong9736]

Question for you on the UL91, does it have a high or low amount of aromatics? And have you noticed the rubber components on your fuel systems drying out and cracking more often/at a faster rate?

[@joelv4495]

​@@michaellong9736 I would suspect cracking to be caused by ethanol in the fuel, not the absence of lead.

[@SuperPhunThyme9]

​​@@joelv4495 ethanol needs to be kept out of gasoline. It's nothing but a scam pushed in the 90's by a lobby of corporate corn growers. Something most people don't realize is the amount of oil and gas burned on the front end to produce the ethanol is kind of insane. If it wasn't subsidized, it would be very expensive, and the expense comes from all the energy (i.e. oil and gas) we use to grow the stuff on a commercial scale.) Fact is, nothing burns less energy than simply sucking a liquid out of the ground. Then there's a whole global chemical industry that now exists on top of that just to produce the additives you need to just *_partly_* protect your engine components from the ethanol.

[@alecbloss153]

@@joelv4495 At least in the US, 91/93 octane fuel usually doesn't contain ethanol. UL91 avgas certainly is not supposed to. I'm a big proponent of ethanol, in the correct applications. But I would be pretty cautious using it in aviation fuels as a general rule, especially in GA aircraft that is carbureted.

[@alexsaab8089]

I don't like flying, but I like hearing Paul talk about it

[@grant9068]

Ditto. Ditto.

[@josh6pack]

Lol. I don't own a plane. I've never owned a plane. I've never flown commercial. I stumbled on one of these videos one day and now I watch just about everything he puts out because how can you not?

[@lharris428]

Same here... will never fly a plane... but I like to listen to people on top of their shit.

[@peterbustin2683]

Thats the one !

[@peterbustin2683]

@@josh6pack Absolutely !

[@alexpitts7634]

Time and time again. The best aviation content on the market. Paul is a legend.

[@reinerressel975]

That was again brilliant Paul , thank you so much . As you mentioned in Sweden we use 91/96 UL since min. 25 years in normal aspirated engines without any trouble with the valve seats , but there is no prevention’s for sticking exhaust valves , because it’s not the lead which let the E. Valve stick , it’s the carbon ( unburned fuel ) !!! If the air/fuel mixture is perfect in idle , the engine will die after start until the parts in the cylinder,head and piston are warmed up to prevent condensation of the fuel . The test of idle mixture show exactly that the air/ fuel mixture is to rich when everything around the cylinders is warmed up .(25-50 rpm rise when leaning) ! To prevent exhaust valve sticking ,piston ring sticking etc. lean the engine 1ore 2 min. after start ( depending on temperature) 1100/1200 rpm lean until the rpm start to go down , taxi with modulating rpm ,try to perform the run up with aggressive leaning ! You can’t forget it for take of ! The engine will die when you advance the throttle for takeoff , if it was aggressively leaned ! Then you have 100 % pwr until TBO .

[@Finder245]

Do you not have 100LL available at all? Do you have to get an STC or some other piece of paper to make 91/96UL legal in your planes? I am just really curious about how this works over there.

[@renhanxue]

@@Finder245 100LL is still available in some places, especially at larger airfields, but most minor ones only have 91/96UL these days. Since a couple of years ago most aircraft won't need a full STC anymore; EASA (EU equivalent of FAA) has a simplified "standard changes and repairs" (CS-STAN) procedure that lets you self-certify your aircraft for 91/96 UL, provided that the engine is unmodified and its manufacturer has approved 91/96UL for that engine (regardless of aircraft). Basically, if the engine manufacturer it says it's okay, you print a supplement page that you add to the flight manual and put some new fuel quality stickers/placards on and you're good.

[@Finder245]

@@renhanxue great! Thanks for the explanation.

[@michaelberry950]

Paul's posts are THE BEST, so creative in delivery

[@therealinak]

One thing I haven’t heard any data on are the thousands of auto gas certified aircraft out there. I’ve got two planes, one powered by a Continental A65 and the other by a Lycoming O-360. Both are approved for auto gas, although the Lyc requires 91. Right now, the Lyc is near 1000 hours, and has been run almost exclusively on a mix of 75% 91, 25% 100LL. Zero issues so far. My A65 is much lower time, still sub 200 SMOH. This engine has been run almost entirely on either straight 87 or the same 75/25 mix the 360 drinks. The story with it is a little more complex; when I bought the plane, Cylinder 3 was an overhaul, while the other three were factory Continental with 36 hours on them. The cylinder was replaced because the spark plug boss hadn’t been properly staked and was backing out. Within 50 hours, the overhauled #3 burnt an exhaust valve and had to be replaced again. Since then, the new cylinder has been flawless. My experience with unleaded has been very favorable. I can’t say I’ve seen any wear on any aircraft I’ve been around, and the vast majority of owners in my little corner of aviation burn auto gas often if not exclusively. In fact, I find with my A65 I’m veritably REQUIRED to run auto gas in the winter: 100LL just won’t pop in those low compression cylinders when it’s -10°F, especially with the Armstrong starter. Anyways, that’s my anecdote. I’ve yet to see much in the way of credible studies on auto gas, although the STCs have been around since I was a child and surely thousands of planes have logged millions of hours burning the forbidden beverage legally, let alone the even more prevalent illegal use. Seems like we could certainly put all the uncertainty to rest with all the logged data on these aircraft.

[@dh-flies]

I just did a quick look up. It seems there are about 200,000 Rotax's flying in the US. All MOGAS Motors. Yes, I'd like to know how many MOGAS planes there are too.

[@SuperPhunThyme9]

Just don't get ethanol in your engine. It's hell on anything rubber.

[@northernandyboy]

And this was just the valve discussion. Then there is the whole vapor lock angle. Keep the videos coming Paul. We are big fans!

[@ziegle9876]

And I also fear cyclic hydrocarbons (aromatics) that raise the octane level, but eat rubber etc.... and your hands.

[@ryanbecker9282]

Another great presentation! I could listen to you talk for hours!

[@dr.dansgarage]

Do we know why Continental hasn't been using hardened exhaust seats? What is the logic/reasoning there?

[@dermick]

Great question - the writing has been on the wall for decades.

[@Logan4661]

Some people (companies) are adamant about being surprised by new regulations, no matter how much warning they have.

[@UncleKennysPlace]

Money. It's always money. Cast iron (or even low-alloy steel) valve seats were very cheap, and sometimes manufactured in-house. The harder stuff is more difficult to machine once installed, and easier to break during installation (and sometimes problematic if "cast in place" due to heat.) But with today's tough carbide and diamond tooling being quite cheap, the actual difference would be ~$20 a jug, most likely.

[@Stepclimb]

@@UncleKennysPlace Kenny’s comment is spot on. Follow the money. If TCM retains the use of crappy valve seats, it can continue to charge for cylinder work and selling more garbage valve seats to customers. I’m sure someone down the line will develop an STC for better valve seats for TCM cylinders if the G100UL actually becomes an issue. Time will tell.

[@RoBert-ix6ev]

They make money with the existing design...Why change?

[@DNModels]

One of THE BEST aviation YT channels ever. Thank you!

[@brucebolla4148]

Just the best! Thank you Paul

[@greensagan]

Excellent research and reporting here

[@rlkinser]

"0% chance" -- any time someone makes a claim with absolute certainty like this, I start questioning everything they say.

[@skar5158]

A very large flight school has major problems and had to stop using it. Entire fleet needed unscheduled inspections.

[@Cheranetube]

Thanks for the excellent insights.

[@bravobob1]

Excellent info. Thank you.

[@MelonJoose]

the world needs more guys like Paul

[@Rift45]

Good stuff Paul! Sounds like there’s some major scamming going on here among the engine makers and the FAA.

[@wolf19511]

Excellent presentation

[@Xanavi]

Toyota could demolish these aviation engine makers. $40k/engine for that? LOL

[@TheOwenMajor]

Unfortunately, because the aviation industry is so horribly over-regulated any competition is doomed to fail. Our one saving grace is Rotax which I'm still amazed they brave the system, I doubt they make much money on their aviation products.

[@TheReadBaron91]

Fed regulation, rampant litigation and low production numbers caused by the former two are the cause of that.

[@harryspeakup8452]

@@TheOwenMajor It's really that the aviation piston engine market is so tiny in terms of annual production that it's not worth Toyota's time

[@crufflerdoug]

Extremely useful info, many thanks.

[@kurtgustafson3346]

That was very well done. Thank you.

[@joksal9108]

A new Paul B video! Best aviation stuff on yt.

[@adeeperbluegreen]

When notification happens for a Paul B video I stop and watch.

[@ronstowe8898]

Great presentation. Love the dialog.

[@tinyskustoms]

Awesome video! So much to unpack!

[@mholzer54]

Hi Paul, I really enjoy your presentation style. Nice work. I no longer fly nor use my A&P license, so I KZbin Fly. Osmotically flying and analyzing the f-ups in maintenance. I wanted to tell you briefly my own experience with valve recession. As a matter of fact, my after school job when attending Northrop Tech for my A&P license, was converting cars and trucks to propane. Now this was in the early 1970s, when fuels were fuels, but we learned to advise customers who converted to propane do so with either a) top end rebuild, including Stellite seats; or b) a squeaky clean new engine.; or c) if you have a Ford, they used to sell factory crate engines, set up to run on gaseous fuels. I have seen, firsthand, what some serious valve recession looks like. I used to own a 1977 Skyhawk, with the venerable O-320-H2AD engine. I personally would not put UL fuel in it without a top end job. My 2-cents and I'm sticking by it. Marc

[@petethecatable]

great job with a complex matter. Thank you.

[@MarkHeckler]

Great information wrapped up with a flourish. 😂 Thanks, Paul!

[@jturner9066]

Well done Paul. We may not agree all the time, but you make this stuff easier to understand. Thanks,

[@richc47us]

thanks Paul....very interesting....even from a former engine motor head of the '60's and '70's when performance was tested on the race track and high compression engines. Looks like material science needs to be always improving esp for piston airplanes.

[@billlyl3725]

Thanks for the Pinto pic! My first car in high school, living the nightmare is right!!

[@rigilchrist]

I've said it before about Paul Bertorelli's work: nobody does it better. Thanks for explaining this so well!

[@MADmosche]

Almost everyone on KZbin does it better than this…they don’t leave constant buzzing noises in their entire video. This channel is very unprofessional.

[@Dysiode]

I've never flown in a small plane, I never expect to, much less own and need to fuel or maintain one, but I still watched through the entire video. Great job presenting the information well enough even a complete layperson can find it interesting! Praise The Algorithm!

[@AlexandarHullRichter]

Fueling the airplane and inspecting the maintenance history are part of flying, whether you own a plane or not.

[@cameronh5442]

Great video!

[@NooneStaar]

One of the best aviation channels I've ever stumbled upon.

[@Captndarty]

What we really need is for Rotax to come out with a larger displacement 180-220hp turbo variant of the 915. Ultra smooth, reliable and loves to sip on 91.

[@TheOwenMajor]

A 199hp Rotax would be revolutionary for GA. The rumors have been floating around for years now, fingers crossed it comes soon.

[@vitordelima]

They tried to release a bigger engine once and gave up, it's in one of his previous videos.

[@rampanswallo]

There is already the UL power 520is and 520T

[@vitordelima]

@@rampanswallo They are air cooled.

[@UncleKennysPlace]

Yeah, they should build a six based on the same technology, then develop an STC for a popular type (say, O-300 powered C172), and give the STC away with an engine purchase.

[@earlfoss99]

Paul is a master at his work. I look forward to every one of these he hosts.

[@MADmosche]

“Masters of their work” don’t leave a loud constant buzzing noise in the audio track of their videos.

[@jamesengland7461]

'Blow out the exhaust port on your pocketbook.' Epic Paul humor, as always!

[@timhuckabay]

Thanks, Paul, for a comprehensive analysis of unleaded fuels in aviation engines. It greatly helped put me at ease with this change. Question: does the UL fuels store as well as the 100LL fuels? Car gas doesn’t store well at all. Thank you

[@pacadet]

Modern automotive fuel doesn't store well because of the added ethanol. Ethanol-free mogas stores just fine, just like 100LL does. Since 100UL is ethanol-free, I would expect similar results.

[@rexmyers991]

Paul - As usual you have presented an excellent (unbiased as much as possible) report on this mess. One thing I’m curious about is: price at the pump in relation to 100LL and how is it distributed from where ever it’s made to the local airport.

[@SebSND]

Man, that one moment at the end caught me so offguard. Busted out laughing loud for it. Thanks for the great Reporting, Paul.

[@gregoryhughes]

Loving the audio in this one

[@cujet]

Thank you for the excellent presentation. I've used unleaded extensively in aircraft engines. My experience is overwhelmingly positive.

[@SuperPhunThyme9]

Just keep the ethanol out at all costs. It's hell on anything that's not metal in my experience.

[@th3b0yg]

Well, I'm glad that's all cleared up.

[@tonysimi5763]

Thx for making the mud less murky Lol. I'm be crossing my fingers as I fill my Cirrus's tanks. I am happy as a lark to have unleaded at the airport for my Rotax powered LSA!

[@ersinc9080]

High quality reporting 👌

[@joeaverage5347]

Fantastic evidence backed sort thru the conflicting rumor! Paul, da Man!!!

[@Dg-zj6jo]

brilliant sir great video

[@MrAvant123]

WE have huge experience in the UK in changing valve seats for classic cars pre-mid 70's it now as accepted as getting a filling at the dentist.

[@joao-pt]

All hail the Great Paul Bertorelli! 🙇🏻‍♂️ Amazing 👏 as always 😉

[@fixento]

It was my understanding that lead additive in gasoline was to prevent knocking, it was not added as lubricant. Preignition can definitely cause damage to the valves and increase wear on the engine. However, electronic ignition and fuel injection system removing the risks of knocking when the correct octane fuel us used. Older planes with carbs on their engine., that I don't know.

[@kr6dr]

I don’t understand why aviation engine technology is so far behind automotive engine technology. My 1985 Honda Accord went 432000 miles with nothing more than routine maintenance. The only reason I retired it was the emission control system had a problem that would cost more to repair than the car was worth, but it was still getting 31 mpg.

[@jameschristiansson3137]

Did you run your Accord near max power for hours at a time very often ?

[@stefanremund8596]

Aircraft engines are behind as far as technology goes, but there are some important things to remember: -Many aircraft engines are air-cooled and designed to be light as allowable. -Your Honda engine may have gone 400,000 miles, but it probably didn't spend much of its life having to produce most of its potential power for hours at a time. -The stakes are a lot higher when an aircraft engine fails vs a car engine, and this leads to a conservative tendency in the aviation industry to go with what is tried and true. -There are few big competitors in the GA piston engine market (really only 3) and they have little incentive to invest billions of dollars when they have seen smaller companies try to adopt automotive engines and fail. AVWeb did a good video about this subject, we might see more modern designs in the future because there is really nothing fundamental forbidding them but the biggest impediment to it right now is inertia.

[@Finder245]

It’s a very different operating environment, and the volumes are not there for a company to spend the money to constantly develop new engines. There are simply not enough new planes sold every year, and getting STCs for all older models is not possible. Even if you could, and everyone bought your new engine, you would sell less than the number of engines GM alone makes in a year. Instead, we have old tech that gets the job done slightly inefficiently.

[@clarkstonguy1065]

@@jameschristiansson3137 This is a total wives tale. It is relatively standard for automotive engines to run 1000 hours at wide open throttle as part of their development testing.

[@TheOwenMajor]

@@stefanremund8596 "Aircraft engines are behind as far as technology goes" - Yeah, like 60 years behind (For Lyconosaurus) "Many aircraft engines are air-cooled and designed to be light as allowable." - Really once you add up all the baffles and the air ducts ect, air-cooled engines aren't that much lighter. The real reason is 1950's era technology for liquid cooling wasn't that reliable. "probably didn't spend much of its life having to produce most of its potential power for hours at a time." - True, but the engines are tested at max power for hundreds of hours. Plus Rotax engines spend most of their lives at peak power. "conservative tendency in the aviation industry to go with what is tried and true." - True, but that doesn't mean they are actually safer. There is plenty of evidence these old certified engines are *not* any safer than newer designs like from Rotax. The catastrophic failures you see in Lycoming and continental engines are stupifying, you would never accept those types of failures in a Rotax. "smaller companies try to adopt automotive engines and fail." - They failed because the system is set up for them to fail. "biggest impediment to it right now is inertia." - If by "inertia" you mean the horribly complicated and expensive mess which is certified aviation then yes. The reality is the system is killing GA. We only see new commercial aircraft and engines because there is massive amounts of money in commercial aviation. That creates the incentive and reward for slogging through the system. There has never been that kind of money in GA, there never will be.

[@patrickpowell2236]

Paul, I love the graphic at 6:44 with 2 Lycoming O-320 motors spinning the wrong way. The amount of satisfaction I have knowing that it makes certain people cringe is more than worth it to me.

[@gregfaris6959]

I really like Paul's thoroughness and aversion to speculation. I learned to fly in Europe (France) 25 years ago, and have flown 172s and 182s of several generations all across the continent, but never heard of an unleaded alternative other than home-builts using MoGAS. 100LL is very easy to get across France (where it's currently about 2.60/l, or $11/gal) but in some countries it's not easy to find, and your choice of airports is limited by the fuels they have available. I have not flown in Scandanavian countries, so maybe the unleaded variant would be commonplace there.

[@renhanxue]

91/96UL is common in Scandinavia yeah, many smaller airfields don't have 100LL anymore. I think 91/96UL is going to get even more common at a pretty rapid pace now, since EASA introduced the CS-STAN ("standard changes and repairs") self-certification process about ten years ago. You don't need a STC anymore, provided that the engine is unmodified and the manufacturer has approved use of 91/96UL with that engine (regardless of aircraft).

[@bill832]

Thanks Paul for another great video!!!

[@AmericanBonanzaSociety]

Great overview, Paul, and I'm inclined to believe your conclusions. I'm surprised you didn't point out, however, that (as you stated ) GAMI tested its fuel for about 700 hours of operation (I was under the impression it was much more) with no issues, and that Continental's testing shows the onset of problems at about 700 hours. Can you address this coincidence?

[@ldnwholesale8552]

But Eddie the expert knows more than the manufacturer.

[@SuperPhunThyme9]

Dang that's not enough....

[@BetterAircraftFabric]

Thank You for that comment ! Glad to see your comment here. Thank you AmericanBonanzaSociety

[@Cuttlefish233]

Thanks for the video. What was that map in the background at about 12:49 Also, no hum when I view the video. Clearly some people are experiencing it.

[@briankenney4287]

Well research and presented - excellent job - One factor you may not be aware of is that a one time use of leaded fuels can protect the valve and valve seats, in some cases for the life of the engine. Continental put out a bulletin in about 1947 on this subject. I was a research engineer for a major oil company when our company removed leaded fuels from our stations. Testing we did supported this one time use had a significant effect in stopping valve seat recession. GM had experience with new engine testing on unleaded fuels causing immediate valve seat recession but not in customers cars that occasionally had leaded fuel but used mostly used unleaded fuel. Testing of a fleet of aircraft on UL fuel therefore is not the same as removing lead completely and permanently. So some of the data you referenced may not be valid to projecting the future in the long run and premature failures may occur. My personal view is that I would run a new engine or cylinders on leaded fuel for at least five hours prior to converting to UL autogas. In the future that option may not be available.

[@AVweb]

Is this documented anywhere? Like to see more.

[@quillmaurer6563]

Fascinating idea - sounds like the lead builds up some sort of permanent protective layer on the engine. Perhaps they could investigate this phenomenon to figure out how it works, then apply something similar during engine assembly. Or use lead or something else with similar effects as a break-in additive for just the first few hours - in that case it would make sense not to continue selling 100LL for that purpose but to have an additive one could put in the first tank or two after a rebuild.

[@briankenney4287]

@@quillmaurer6563 I think the lead is needed to allow the seats to work harden in operation. Lead substitutes were tested too and i would not put any of the ones we tested in an aircraft, especially sodium based ones

[@jlorenz55]

Paul, Great video, I look forward to each. How about a video on the new glass panels vs round gauges, are they reducing IMC accidents or spatial disorientation?

[@crawford323]

How about a piece on how the rage in glass cockpits cost almost as much as a new engine and are driving the cost of aviation up to the point that it is impossible for all but the wealthy to fly any more. Give me analog gauges any day. The only glass I will have in my old bird is an iPad. The cost of certified engines plus glass equals six figures $$$$$ in even a kit version of an aerial Putt Putt Puddle Jumper. Who care right? I guess when you are raised on video games you are just not comfortable or confused with what round gauges are telling you. Guess I’m square. I’ll take a six pack of round ones and a good scan any day. At least know where to look to get the information I need. Glass cockpits kills. Let me explain. The consistency of where and how the information is displayed in modern cockpits are anything but consistent between different panels. That right there can kill when transitioning from one aircraft to another. That plus the pressure of rapid fire ATC communications in a real turbulent vibrating vision -blurred eyes -wet -with -sweat IFR/IMC environment seems to be putting down a lot of new glass birds, whether the glass is in the cockpit or wraps the super critical laminar flow airfoil on the wing. One more bit of tidbit. GPS can also kill. When I trained for my instrument ticket, we had to have three altitudes we had to fly: Obstacle clearance. Pay attention to those blue numbers, somewhere in that navigation square is something sticking up if you stray lower than the blue number. Next you had to fly an altitude were you could receive the signal to navigate and finally you had to fly at an altitude to communicate. If you did your homework and the ceilings were lower than the blue numbers, you didn’t go because your VOR needle had a big red flag on the dial. This kept a scud running to a minimum. Not so with the GPS tied to synthetic vision. Pilots have real big balls now. GPS and synthetic vision are not limited to any such height restrictions so scud-running is at an all time high. Inadvertent flight into IMC my ass! Combine that with a glass wing which gives little or no stall warning. Stall/Spin accidents are more frequent now more than ever. Darwin wins. Glass cockpits invite stupidity.

[@jlorenz55]

@@crawford323 I agree about none IFR planes or flying VFR, they don't need them. I believe that the new instruments need to have the functionality to have them warn you visually and audibly about flying below set blue line, DMMS, altitude restrictions, etc. that round dials would not be able to do and that would help with stall/spin accidents. Plus have the panel correlate on the moving map your altitude and the height of the objects in your path and visually and auditable warn you like the TCAS does. Scud-running is always a risk and their training should have kept them from doing it. I'm wondering if the IFR/IMC training is not keeping up with the glass and upset/spatial disorientation training with glass to keep you alive as we're still getting way too many IFR spatial disorientation accidents. The no stall notification wing is a different subject but the DMMS visual/auditable warning would help help with that and save lives. I'd love to hear Paul's take and the research he always does on a subject.

[@singleproppilot]

@@crawford323 Hogwash. Good mechanical instruments were never cheap, either.

[@tissuepaper9962]

@@singleproppilot yeah, honestly I don't think this guy understands (or is willing to admit) that the glass cockpit is doing a lot more than just representing the information you would find on your six-pack. Mechanical instruments simply can't compete with modern avionics for reliability, accuracy, and calibration stability. Obviously I think everybody should *keep practicing* how to fly with just that six-pack, but the data is crystal clear about the fact that glass cockpits prevent accidents.

[@marsgal42]

Following with interest, but a moot point until I can actually get G100UL at any local/regional FBO. My Musketeer's O320-D2B (factory rebuild installed in 2021 so all the modern goodness applies) is approved for the MOGAS STC, but the rest of the plane isn't.

[@majorchungus]

Your video has static when listened to on headphones. I enjoyed the video. I might have missed it but if I have a lycoming engine built in the 50s, will UL100 cause valve seat issues?

[@DougWinston]

Really Continental? Nobody demanded hardened exhaust valve seats? This explains why I’ve never been able to get more than 1000 hours out of a continental cylinder exhaust valve no matter what fuel I run: E-225, TSIO-520 in 2 different T210’s, O470. I ran auto gas in the first and last engines, no difference in exhaust valve longevity. I will be requesting hardened valve seats from now on. Thank you Paul for this very informative video.

[@bobroberts2371]

I wonder if Cont not moving to hard valve seats / valves has something to do with needing some sort of engine modification approval that they were not willing to go through? ( I come from the automotive world not aircraft so I don't know the regs. ) Change the seat material and you need to change valve material. Change valve material and you might need to change valve guide material too. Then you are left with possible differences in expansion rates leading to dropped seats / guides / stuck valves.

[@specialopsdave]

Cars had an identical problem with this in the 70s. We have non-toxic lead substitutes nowadays to solve this problem for those who don't want to retrofit hardened valve seats into their engines

[@Autopilot_Austin]

You always tell it like it is! I like that!

[@pstol53]

My goodness, that was deep.

[@samfischer3897]

Forget about unleaded... I wanna know how Cirrus planes can be fueled with the gas cap on! Think of all the fumes we'd avoid!

[@andrewnardo1021]

I stumbled on this video and I come from the classic car / truck end of things and this debate (along with the whole ethanol debate) comes up frequently. From what I’ve always understood was the valve seat recession panic came from a specific set of GM engines (I can’t remember which ones) that did show valve recession around the time of the switch to unleaded fuel, however it’s also common knowledge that during the late 60s and early 70s US auto makers were really trying to cut corners to compete with Japanese and euro cars. So with that being said it wouldn’t surprise me that a generally softer head material was used and the valves would have recessed anyway, it’s just coincidental that there was a fuel switch during that time. I’ve never run lead additive in any of my stuff. I have a 63 f100 with a 460 out of a 70 Lincoln (pre smog high compression heads) and have had 0 issues. I recently pulled the heads to address a head gasket leak and everything valve wise was fine. I have a 42 ford 2n tractor that has been plugging along on pump 87 for god knows how long and has never smoked a valve. My friend runs non leaded in his late 40s and early 50s packards and Hudson. Moral of the story, I feel while there may be a slight about of truth to the whole “lead lubricates” argument, I don’t feel it saves valves. Valve recession, in my opinion, is cause by bad materials and generally bad fuel, but not the lack of lead.

[@wallacegrommet9343]

Wasn’t the introduction of stellite valve seats the solution to the recession problem?

[@BetterAircraftFabric]

Not at the high temperatures that our Lyc and Conti engines use! - it works fine unleaded only if the cylinderhead is small enough and cold enough, Water cooled.

[@wallywally8282]

Well put fwd👍

[@neilrobinson3085]

We've been using Swift 94UL in our family's 3 airplanes for 5 years now with no problems, including one of the engines making it well past TBO before O'haul.

[@UncleKennysPlace]

Continental or Lycoming?

[@dh-flies]

That stuff is disappearing faster than it appeared because of price. Every airport that used to carry it within 200 miles on me with the exception of one, dropped it.

[@kalilay]

ahh youre one of the people who thinks O'haul is a more efficient way to type overhaul. very cringe

[@maximpikalev9538]

nice video, though there seems to be a problem with the mic, there's an audible buzzing noise throughout the sections when you're speaking

[@silasmarner7586]

I didn't hear it but I guess I'd better listen more closely.

[@singleproppilot]

It was the first thing I noticed, too.

[@jeffpiatt3879]

The Pixie graphic was a nice touch. 😄

[@thearchitect4726]

also happened to exhaust valves in lpg and cng fueled vehicles. hardened valve seats and stainless valves fixed that

[@Mentaculus42]

It is interesting that the Ford CNG engines that are certified to be converted to CNG in California have improved valve seats installed at the factory and are delivered as conventional auto gas engines and then converted to CNG at a certified third party facility where all the external CNG equipment is installed. So that more than suggests that CNG as a fuel is more demanding. The rather vagueness of how this new fuel will perform in all possible combinations of uncertified random engines that are still operational should at least give a few people sufficient pause to be cautious and do the necessary vigilant checks.

[@ScottSmith-dd6iy]

Intake valve seats do wear also, lead is good for octane. any engine with hardened valve seats usually hold up well, however the valves sometimes will wear significantly on the valve face. So pick your poison. Low sulfur in fuels has been known to wipe out valve guides. So the bottom line here is.. if your engine has been properly built or modified to run on unleaded fuels, it should, "should "have the proper parts with the proper metallurgy to perform well on unleaded fuels. That being said, a stringent maintenance of the valve tip height will give you some idea if any accelerated wear that is happening. As with anything that performs a particular task very well, the Government will find a way to take it away. Some will hate it and some will love it.

[@onethousandtwonortheast8848]

Paul is the best.

[@joebledsoe257]

Nah the metal alloys used for valves have been updated to live with unleaded. The lead originally started out as an anti knock component for the gas and ended up being a cushioning agent for the valves as they landed on the seat. So the alloys have changed and that should be all that’s required. Valve springs also changed.

[@2caver]

Thanks Paul. Although I fly Rotax using non-ethanol auto fuel I'm still interested in 100UL. I have 875 hr on my 912 and have had no problems, :)

[@rubiconnn]

I'm not a pilot but I've always heard good things about Rotax engines. I have one in my old BMW motorcycle. I wish they were used more commonly in other situations.

[@kevinkelley3657]

The FAA did a study years ago on valve recession, and the study found that lead did nothing to prevent valve recession other than raise the octane of the fuel. Valve recession is caused by pre-ignition. Pre-ignition is caused by inadequate fuel octane rating. Lead does not magically coat valves and prevent exhaust valve damage, lead does do a good job of raisng the octane of fuel.

[@CatarineausArmory]

For further research one could look into the part numbers of those cylinder seats and cross reference to different cylinders/engines's for conformity to what Continental will not confirm. Not so sure the exact material and processes would be readily available.

[@slanis6718]

Paul, could we get an update? Recently (as related to the time of posting) the University of North Dakota switched their fleet back to 100LL following valve recession problems while using Swift Fuels UL94. What’s up?

[@carmencrincoli]

Paul, the thing I always appreciate about your content is that while you look and sound like someone who really believes things were better "back in the good old days", your content is impeccably researched, and you have little respect for anything that isn't backed by data. It makes for some delicious sarcasm, and REALLY informative content. 😂😂

[@leeross7896]

I always did like Lycoming engines better now i know why :) wonder how much it would have cost continental to provide hardened valve seats before 2017? when the average overhaul is 35 to 55k I cant imagine it would have been that hard to pass the cost along to the customer.

[@dagabbagool2600]

If it comes down to it, tetraethyl lead is available to purchase online from overseas.

[@iancormie9916]

It will be interesting to see how long it takes for unleaded to remove the lead deposits in existing engines. It will also be interesting to see what octane ratings are really needed once those lead deposits are gone.

[@eloiseharbeson2483]

I remember this very argument 40 years ago as to older motorcycles. The large-scale exhaust valve failures predicted were never seen. I don't think any motorcycle engines used rotating valves.

[@kirya312]

I'm pretty sure most automotive engines have valves spinning by design after certain rpm. So, motorcycle engines are probably the same way?

[@togacruiser]

I overhauled my Continental 90hp engine using new Superior cylinders and new crank. I never used 100LL or straight mineral oil. I used alcohol free unleaded auto fuel and Aeroshell W 80 for the break in which took less than an hour. 6 years later the engine has 710 hours with great compression and so far I have not had to add any oil during the 30 hours between oil changes. One note: on several small Continental engines if I switch to multi grade oil I start getting lifter ticking that can be heard in flight. Switch back to 80 or 100 Aeroshell W and it goes away.

[@jackielinde7568]

At 7:00 those engine illustrations look like Corvair "flat 6" engines, although I suspect they're more like Boxter engines.

[@berlinberlin4246]

Thank you for pushing the movie to UL gas! But just a Feedback on the Audio: I can hear a 60Hz humm in the background, no Dealbraker but unpleasant.

[@chuckkemp6879]

Audio was clear on my viewing via PC

[@Miksa]

Would it be possible to do a FOIA request for the PAFI testing documents?

[@paulricketts1089]

.....being an AirCooled VW/Porsche Mechanic, back in '7something, when they removed lead from pump gas, we were freaking out over just what you're talking about now. We thought we'd have to replace valve seats and valves. As it turned out there was NO effect at all. And now 50ish years later I still remember worrying about nothing. I can't see Aircraft engines having any issues either.........

[@donaldmikulec4332]

In 1982 I bought a 1974 Audi that had split exhaust values. I believe the engine was designed for leaded gas, but had been running unleaded. In the summer of 1983 I replacing the cylinder head. The car ran great for couple of years. In 1985 I started to notice slipping performance again. The car was totaled in an accident so I didn't have to replace the head again. My dad said the split exhaust values was due to running unleaded gas in it.

[@willwaconsya3433]

For years and years Amaco had lead free gasoline. Long befor other brands went lead free. It had an octane of 95. My Dad use to run it in his vehicles for years. Also in the lawn mower, motorcycles, or any engine. Instead of lead they were using a chemical called “ Nichol- molibdium” to lubricate the valves. I may have spelled that wrong. It never went stale when stored. Or turned to gum. And the high octane never pitted the pistons of small engines. It was also great in 2 cycle engines. It was a great fuel. But in time went all others went lead free they changed the formula in Amaco gas. It’s not the same fuel anymore. And I believe all lead free gas is the same except for the added cleaning agents. Aviation fuel has extra components added to prevent boiling at higher altitudes. I have found that for automotive fuel EXON has the best cleaning agents to prevent carbon build up under the valves. The Ford eco boost engines are prone to carbon build up due to the way the emission system works.

[@tomcoryell]

Hey Paul, Thanks for confusing us with the facts!😎

[@johnfitzpatrick2469]

Great technical detail. What about the alloy and the valves selected by the engine manufacturers. 🕳️💥💰