Long-term MPG Update on My 2024 GMC Sierra 2500 HD Gas 6.6 L8T & Allison 10-speed

[@scottmcgraw1603]

I just did my first trip on I70 and got 19.2 for 230 miles from Ohio to western Pennsylvania. Gas 6.6L 2024 GMC Sierra 2500hd.

[@AdventureRocks]

Very impressive, thank you

[@chadmiller6487]

I get between 18-19.5 in my 3500 drw gasser

[@BabyGators]

It’s kind of amazing that all of the new technology and costs haven’t netted but minimal efficiency gains over the last 10-15 years.

[@JB-ej8zy]

I think part of it is the trucks keep getting heavier

[@donraptor6156]

My 2015 Ford f-150 4wd with towing package does 24 around town. It does about the same on the highway

[@AdventureRocks]

I hear you. I am probably in minority, but considering I get as good, if not better than my 2005 F150 5.4 Triton, I'm content with the larger L8T.

[@BabyGators]

@@donraptor6156 what motor is that? 3.5’s barely get over 20. Also I was primarily talking about HDs

[@Icutmetal]

It IS kind of amazing though, that newer trucks have all this technology, increased capability, more power, better drivability, increased weight, (the list goes on), and manage to maintain that gas mileage.

[@TheFlooringInspector82]

2024 GMC 3500 (SRW) SLT 6.6 L8T 10 speed, and I have about 7,000 miles on it so far. No oil consumption so far, it's my understanding they resolved that issue but I could be wrong. I have not modified my exhaust or intake in any way, the only thing I have added is a tonneau cover and my recent trip from mid Maine to up state New York and back I averaged 15.9 mpg and that was not towing. That was just two adults and luggage and a few tools in the bed. Was going out there to do an inspection workshop and visit a tradeshow. Overall, I am impressed by this truck so far. Very comfortable, good capability, reasonable fuel economy for what it is.

[@AdventureRocks]

Very nice! I'm with you, very pleased with the economy.

[@mikepayne2572]

I have a 2024 GMC 3500HD 4x4 Std bed. I have just over 4k miles. I have checked the oil every 1k miles. Absolutely NO engine oil lost. Thanks to you, I installed the BORLA exhaust. I love it. Your videos are excellent. I am getting 11ish MPG in heavy, hot (phoenix, AZ) city traffic. 14ish MPG on all freeway at 75-80mph. 15.5-16mpg at 70mph. The Borla exhaust had a problem with my truck. The system came in 3 sections. The front pipe (closest to engine) does not fit my truck. I contacted Borla with my VIN. They did not have an answer. I'm wondering if the 3500 is slightly different than 2500. I had an exhaust shop custom fit the front section, so everything works great. Borla even sent me another pipe but it was also incorrect.

[@AdventureRocks]

Thank you. And thanks for detail on 3500 exhaust. I did not realize they were different. I still really like the way it sounds.

[@danthompson1467]

My 2011 6.0 gas 2500 he 4x4 with 287654. Miles gets 17- interstate 15.6 average 12-14 towing I think I will just keep it . The new trucks have nothing but problems 👍👍

[@AdventureRocks]

Great point. If it ain't broken, don't fix it right?

[@NickRas625]

That's amazing... Never seen better than 15 unloaded in my 2018 6.0

[@Ajp05016]

This is a money set up the color scheme is nice everything goes together the MPG results are good as well

[@flamarlamb]

I have a 2020 F250 XLT 4wd Crew Cab Short Bed withthe 7.3L gas and 3.55 gears. In the summer, unloaded, I’m getting an average of 15mpg plus or minus with about 15% town, 25% Interstate, and 60% country roads. It’s South Georgia so some small hills but mainly flat’ish. I routinely get over 16 miles per gallon when I drive from Vidalia to Hilton Head Island and back. I did two cross country trips with a 7600 lb Airstream, to San Diego and to Denver, and got 9.5 mpg average for each trip for the entire trip. I’m pretty happy with a gas mileage. I get with this truck

[@AdventureRocks]

Very nice. Those are solid results.

[@thephoenix1117]

Hey, I've been following your channel for a bit since I have essentially the same truck. Appreciate the content, I've been comparing my truck stats to yours. I have a '24 SLT 2500 HD - 6.6L/10 Speed w/full Towing and x31 off-road package. Bought it in March of this year to tow a 30ft Rockwood Ultra Light . Dry weight just under 7000 lbs. Loaded, probably about 8200 lbs with 5-10 gallons in the freshwater incase its needed on the road. All other tanks are emptied prior to transit. I dumped the factory oil at 1000 miles and sent it into Blackstone. It came back normal for a new engine. For the second oil change I used AC-Delco oil that I got from the local GMC dealership (I had a coupon for a free oil change and filter). Then, at about 1800 mi, we took the rig from the Chicagoland area to the Badlands and Rushmore/Custer state park over the week of the 4th of July. We bucked a headwind the entire 2 days of driving and my gas mileage was about 7 mpg heading straight west. On the return trip, I got about 9 mpg with the tailwind. And I drove for stretches (in both directions) at 73-78 mph. South Dakota, the 80 MPH speed limit is a mere suggestion so I pushed things a bit to not be a stationary object on the Interstate. Anyway, I dumped the oil again when I hit 5000 miles about 2 weeks ago and sent that into Blackstone as well (results pending. They are not quick) ... Being an old mechanic and into car restoration, after some research, I've settled in on using Pennzoil Platinum Full Synth 5w-30 Dexos-1 with a Mobil1 oil filter. I used to be a Castrol guy with my Tundra (and other cars), but upon further review, the Pennzoil seems to be best in class these days. Fuel economy average at the 450 mile distance is 12.1. Average at the 5000 mi point that includes 1900 miles of towing the 8000 lb rig, the truck is 11.8. I see some posts about 15, 19 mpg... Unless you're driving downhill with tailwind, I can't ever imagine my truck sniffing anything above 14 Mpg with no trailer, or 10-11 with the rig in tow. As far as oil consumption, so far, what has gone in, has come back out. No measurable oil loss so far.

[@AdventureRocks]

Thank you. That is great input and feedback on MPG and oil. I just changed oil with the Pennzoil this go round too. I'm with you on some of the higher than normal MPG results posted online...not getting those myself. Maybe if hyper-miled I could, but not in regular driving at least. Appreciate the comment.

[@thephoenix1117]

@@AdventureRocks - From my previous post, Blackstone results from the 5k change were normal and within spec. Comments were "this looks like a healthy engine with nothing in the oil to indicate there are any potential problems". All good there. --- I just returned from a Labor Day trip (about 10 days). From my driveway - just north of Chicago - to the FL panhandle to visit family (Destin/Fort Walton Beach area), then up I65 to Mammoth Cave KY for a few days and back to home base. Rig and items in the bed estimated weight - call it 8200 lbs ( full 35 gal tank, 5 gal reserve in the bed, along with golf clubs, firewood, extra propane, Tools/jack, etc... and about 5 gal of freshwater on the rig for road use plus food/drinks, clothes and cooking items. Trip summary, 2468 mi - 7.8 mpg - 50.8 avg speed. That total also includes about 250 miles of driving the panhandle with no trailer. KY and AL ungulate a bit so there were periods of hard acceleration, topping out at about 4400 RPM during some of the steeper climbs, but overall cruising speed of between 68 to 75 mph saw anywhere from 1800 to 2800 rpm depending on the gear the trans decided to settle into... Used Tow/Haul whenever I was pulling. Looks like its settling into just under 8 mpg when towing. Not planning any more trips this calendar year, so I'll reset the trip odometer and get some metrics now that the engine has over 8k on it and I'm not towing anything for a while. See what it looks like over a longer period of time with a mostly empty bed and nothing hanging off the hitch.

[@AdventureRocks]

@@thephoenix1117 That's about as real world as it gets! Very helpful.

[@edkruzel]

I don't think anyone with a truck looks for subcompact, hybrid type milage, but I do think we all look for the best milage for the capability of the trucks we drive. My 2020 Ram 1500 averages about 17mpg, but at 80% of its tow max, and running at 65mph, I still average 13mpg, 14 with the wind cooperating.

[@matthewanderson9912]

I think 14-15 mpg is very doable for empty daily driving. That’s what my 2022 gets. I don’t think the purpose of the 10 speed was fuel mileage though. I think its purpose is better drivability with its closer ratios to keep the engine wound up in its power band more. My 2022 is over 48,000 miles now. No oil usage. I do change oil at 3,000 miles and have since it was new. But non usage. I get 8 quarts or very close to it out at every oil change.

[@predator-1]

Driving style/habits have the single greatest impact on MPG

[@AdventureRocks]

Good point. I am guilty of giving it the beans to hear the exhaust note from time to time.

[@dixienormous9052]

I have a 2019 Chevy High Country 6.2 10 speed tranny 9K total miles Our last trip I-84 in the gorge 1000 miles 23 mpg 75 mph Our last trip towing a 8K trailer 10.8 mpg The one trip towing the trailer before was 9.0 mpg The best I ever got on I-5 south 25 mpg

[@AdventureRocks]

Great input, thank you.

[@johndzurenko]

Nice real world mpg of an hd truck

[@JacobWinkle]

2021 Chev 3500 6.6 Gas 4WD Z71 Crew Cab with 8ft bed 65MPH 15.9MPG Unloaded 9.3MPG-9.5MPG Loaded Trailer-3600lbs Unloaded Trailer-13,600lbs Loaded Towing a 259D3 Cat Skid Steer This is all with the 6 speed transmission. Personally, for roughly 2MPG difference compared from 6 speed to 10 speed. I personally wouldn't trade or get another truck just because of the transmission alone. My personal opinion of course but also my results comparing to your results. I've done a trip from Oceanside California to Glendale Arizona to pick up a cabinet for a jobsite and I've done my fair share of unloaded and loaded driving. Being business oriented and construction, I'm always watching my profit margin and MPG/ gas prices are a big deal for me to pay attention to and know what is getting spent and how much and why. Thought I'd share for others who are curious as well and hopefully this helps.

[@AdventureRocks]

Thank you for sharing

[@tj549]

2022 Silverado 6 speed . About same weight bumper pull RV trailer. My numbers almost mirror yours. Also use it as a daily driver 30 miles a day.

[@sam-68-56]

Was trying to see what your tire pressure was and I think if you bump up the pressure a little your mileage will be a bit better.

[@danieldilts7323]

that MPG information is very helpful - now I know I will keep my 6.0L Vortec going because it gets as good if not better gas mileage and i don't have to pay 60 grand for a screen to tell me that

[@AdventureRocks]

If it ain't broke, don't fix it, right?

[@brucesheehe6305]

My Duramax gets 19 to 20 mpg unladen. But is costs $10,000 more and has lots of emissions equipment to deal with. I would go with the gasser next time.

[@AdventureRocks]

Great point. And, vey insightful. Always trade offs, right?

[@garrettghent2061]

My 2022 F-350 powerstroke SRW gets 24 highway unladen. About 18 around town. And when I need to I can tow 20k.

[@jeremykern9071]

2024 AT4X here with the 6.6 gas and 10 speed, getting about 11.5 all around, but it does have bigger tires and a little lift to it. I see that you solely relied on the trucks MPG for your video, have you hand calculated your MPG? Some vehicles are way off, but I will say my hand calculated MPG is usually within 0.2 of what the GMC reports.

[@AdventureRocks]

Great question. Yes, I have found the same on mine. Truck MPG is very accurate compared to hand calculation, especially on the longer runs/full tank calculations.

[@NNWarrior]

I have a 2024 2500 6.6 Duramax. Last night I got my best MPG at 24.7. Before that was 23.6. I had a 6.2L gas before this one and it was never above 15mpg.

[@AdventureRocks]

Dang that's impressive. Hard to beat the diesel duramax.

[@NNWarrior]

@@AdventureRocks this is my first diesel truck and I’m very happy with it.

[@rapidride2]

​@@AdventureRocksDon't forget to factor in increased diesel fuel costs. This definitely tightens the competition.

[@AdventureRocks]

@@rapidride2 for sure

[@ls1jeeper]

All of my trucks are now gas, about the only thing I miss is an engine brake and that's all. Pretty much most diesel trucks are junk now unless they're deleted.

[@AdventureRocks]

Good point. I do miss the engine brake sometimes too.

[@salcacho8381]

I have new 2024 6.6 gas and pulling a 20 ft travel trailer from Vegas to Boise Idaho I didn’t get any better than 11 miles per gallon

[@AdventureRocks]

Thanks for sharing. 11mpg is pretty good for towing.

[@osrr6422]

~12.7 consistently. I've seen 13 on long highway trips. I didn't buy it for MPG, that's what the 4 banger work car is for.

[@AdventureRocks]

I hear you, totally agree.

[@ericj810]

Ya mpg isn't something to get upset about on a gas 3/4 ton truck. Especially towing. The chevy 2.7 turbo does a killer job on the 1500. But even it will dip in mpg when ya drop a 8k camper on its rear end.

[@bigmurph1447]

I have a 2024 3500 crew cab long bed i have over 8k miles on my truck. I keep track of my fuel mileage last tank i got was 15mpg. I live in Pennsylvania the roads are not flat. But i do take notice the 6.6 is sensitive to what type of fuel you run.

[@backyardscaler]

What octane fuel?

[@bigmurph1447]

@@backyardscaler I run 87 or 89. I run snappys fuel

[@prettybadboylagerberg6385]

Hi Justin. Love your videos. Have you double checked your mileage with actual gallons/miles math? I’ve got a 23 HD with the 6 speed and my overall mileage since the beginning (17k) shows 11.5 as well. But, I’m on a big road trip now and the trip computer is overestimating between .6 to 1 mpg on 3 fill ups so far. And we had similar results towing over 4k miles last summer. It’s frustrating that mine does this. I’d rather it underestimated. Peace brother.

[@AdventureRocks]

Thank you! I hear you on the frustration, epsecially over vs under. I don't manually calculate a lot, but the few times I have I'm about ~1/2 mpg under or over...usually my computer seems to be more pessimistic. I may have failed to mention but when I showed the overall lifetime average on mine in the 11s, mine is kinda misleading as it has the towing mixed in, but I figured I'd share just as a reference overall. My average tanks with daily driving are high 12s and low 13s unladen. If I'm behaving on the highway in the 16s and around 9 towing. Hope this helps. And appreciate your helpful reference points.

[@jimcollins8097]

I have a 2020 2500hd gas, and my computer consistently gives mpg that is 10 % better than manual calc. I am 11-12 in town, 15 interstate at 80 mph, 16+ at 70 mph, 8,5 towing 4 ton travel trailer on hiway. It's all about speed, wind drag increases by velocity squared

[@puma93]

Drive about 100 miles a day for work. Was interested in one of these 2500s but was wondering how many miles you can get on a full tank? If it was a 36 gallon tank I figured around 550 to 600 miles averaging 17mpg but I'm yet to see those numbers in anyone's video. It's usually around that 380 to 400 miles topped off.

[@AdventureRocks]

I hear you, great question. I agree with you that 17mpg is likely more idealistic in terms of consistency and real-world use. Based on my first 7K miles on truck if I was doing a 100 mi highway loop in the 50-60mph range I think I could probably get 16-17mpg on that highway portion under ideal conditions. But, if I went over 60mph or closer to 70mph, then I'd likely get closer to 15ish. So depending on speed I think 15-16mpg on highway is more realistic for an average...some days it might be 17-18 and others 14-15, but average 15-16. Factoring in a buffer of about 5 gal on tank to empty, that leaves 31 gallons so about 500 mi of range, again under more ideal circumstances...attainable, but gotta watch the speed and feather it. I'm glad GM put a 36 gal tank as that at least helps with the range compared to a 30 or 31 gal...few extra gallons can make a big difference.

[@clintpeterson9028]

About right

[@kirkdunn1379]

think i may be moving to a 24 from a 23, not necessarily for 10spd but for multiple reasons, main one being tax writeoff for this year and I miss the multi pro tailgate while working....the tranny and new infotainment will be bonus as I had it in a 1500 as far as the gas goes, these HD hate stop and go.....highway is totally fine and towing IDK as I haul heavy weight in the bed, never towed anything some deals are popping up....seeing aroud 5k off sticker

[@AdventureRocks]

Hope your new purchase/trade goes smoothly 💪🏻

[@sam-68-56]

I just took my 2024 2500HD in for the tailgate recall. They had to order the switch then contacted me when it came. When i took it in there was another recall for the trailer brake module and they performed that for me also. Did yours have the trailer brake module recall? It showed up when I looked at my GMC website.

[@AdventureRocks]

@@sam-68-56 yes, I need to find time to do the trailer brake module recall. I think that one is more recent, or at least it just showed up for mine in last month or so. My hope is it'll fix the back feed issue related to solar and lithium with slightly higher voltages.

[@jayb7675]

My 24 Duramax Crew Cab 3500 with 37s and a 4 inch lift gets 13mpg. That’s mostly city driving.

[@AdventureRocks]

Thank you for sharing. I bet that's a sharp looking truck and great stance too.

[@clintpeterson9028]

I have 2022 hd custom mpg empty 17 loaded under 10 thousand lb cargo 14

[@mkimber]

Nice truck but thats pretty bad mpg. My 1 ton 2019 duramax gets much better towing and empty. I was considering trading for the 6.6 gas but think I'll stick with my l5p. Thanks for the honest video!

[@Icutmetal]

I have a 2018 Duramax and set aside the power/torque argument, I’ve done a lot of calculations for TOTAL COST OF OPERATION (fuel cost, oil changes, DEF, fuel filters, etc, etc (I’ve tracked all of it over the last 160k), and as long as the fuel cost disparity isn’t a lot, the gas will break even for me at ~14-15mpg average.

[@shettlock]

What about your 2nd most common question aka the oil consumption question ? No burn/ blow by?

[@AdventureRocks]

Great question :) Yes, I've been checking regularly on the dipstick and it is still in the shaded so far. I am going to do 2nd oil change in a few weeks and plan to measure out the oil I drain as I'm curious how much is left too. I haven't noticed or smelled any burn yet.

[@benvanbronkhorst6531]

My big box van GMC im getting 12.9 according to the computer on the van it's a 6.6 with the Allison trans

[@AdventureRocks]

I didn't realize they offered it in the van, thank you for pointing that out...what a nice upgrade for that model. Sounds like we're about the same on MPG.

[@craigjones3846]

Reckon GM will update the body style to compete with F250 anytime while most of us are still alive? I’m a GM fan but my next truck will be an F250 if not and I got a Tacoma for daily work driving in 2018.

[@AdventureRocks]

I hear you! I get that the appearance is subjective. I may be in the minority, but I actually really like how the 2024 refresh looks on the GM HD trucks...it's one of the few trucks that I think looks good from every angle. But, I realize that is only my subjective opinion. Ford looks sharp too, especially upfront with the new refresh last year.

[@Knight21030]

The current T1 platform will be 6 years old next year... If I were to read the GM tea leaves, I would hazard a guess that they're going to update the platform in '26. That's a ways aways so, if you want to go for the F250, I'd go for the 7.4 gasser 👊

[@michaelbefumo-qg7ji]

It's also the weight of these trucks a 1988 Chevy 2500 weigh 5000 lb

[@AdventureRocks]

Great point

[@wildwilliesadventures]

Have you leveled the truck or installed air bags?

[@AdventureRocks]

Not yet. I'm probably in minority, but I actually like the factory rake, especially how it levels out when I tow it haul heavy.

[@M_dot202]

​@@AdventureRocksyou actually use your truck to tow...please don't level it.

[@edwardmachado4314]

What is your payload if I could ask thanks in advance

[@AdventureRocks]

@@edwardmachado4314 3314 to be exact

[@justinevans9785]

What octane fuel are you using? Do you use ethanol free fuel? I have a 2018 1500 with a 6.2l . I run premium ethanol free 91 octane I get about 3 more mpg than I do with just premium 91 octane fuel.

[@AdventureRocks]

Great question. The L8T truck engine is not as much performance-oriented compared to the 6.2L with higher compression ratio, so the L8T just takes regular octane, 87 per GM recommendations. There's a lot of opinions out there running higher octane vs reg octane on engines that don't require it, but in my experience on L8T at least, the increased cost of premium negates any marginal fuel economy gains. But, that'll be different on 6.2L given compression ratio. A lot of opinions and preferences out there for sure on this topic! Again, great question!

[@emmanuelhatziminadakis1797]

The 6.2 and 6.6 have similar compression . 6.6 differs by having direct injection.

[@justinevans9785]

@@emmanuelhatziminadakis1797 The 6.2L L86 and L87 are both direct injected

[@ada-yw1bb]

​@emmanuelhatziminadakis1797 Uh.... No , 6.2 has higher compression, and they both have direct injection.

[@mikezahnow1605]

Ford f350 6.7 power stroke all the way boys.

[@fattie2550]

Dang…I wonder what the ford 6.8 gets with 3.73 gears.

[@AdventureRocks]

I wonder too...I'd guess about the same or close? But, it's not as popular as it's my understanding the 6.8 is limited to XL trim.

[@fattie2550]

@@AdventureRocks you can get 6.8 in XLT and it drops the price 1750.00

[@AdventureRocks]

@@fattie2550 Did not realize they opened it up now...thank you. That could be a nice savings.

[@westcoastronnieOC714]

Miles per gallon is going to vary on each individual person. How heavy you are how fast you drive if you're towing do you have fast takeoffs at lights etc. So miles per gallon is just an estimate don't ever go buy a window sticker about miles per gallon. First of all if you have a truck and you're using it as a truck miles per gallon shouldn't really matter anyways. Nobody's buying a truck for miles per gallon.

[@AdventureRocks]

Great point, right tool makes all the difference, right?

[@edwards6431]

2500 AT4X and I get 9 to 12 MPG

[@AdventureRocks]

I love the at4.

[@JoeyO123]

Why worry about mpg when you buy a 2500 6.6 L truck? $80k truck and concerned about mileage, buy used Hugo or vw. If you can’t afford the gas you really can’t afford the truck.

[@AdventureRocks]

Exactly, 1:05. But, I personally think it's more about expectations...folks considering going from 1/2 ton to 3/4 ton or diesel HD to gas HD...a lot of people just want to know what to expect in the end.

[@wdhigh77]

It’s not actually worrying about mpg. Mpg is directly related to useable range. Pulling our 37’ trailer with our gas truck sucks when trying to fill up on the road. That being said we don’t need diesel, but damn if it wouldn’t be nice pulling through the truck lanes every 200 miles vs, dodging cars at the stations not great for trailers.

[@AdventureRocks]

@@wdhigh77 Great point.