I Try Again...Highway MPG Test with My 6.6L L8T Gas Engine in 2024 GMC Sierra 2500 HD

[@SuperSnakePlissken]

16.6 is what I average usually in my Tundra V8 4x4. I tell you that because you are clearly doing pretty darn well in a truck that size with that big of a motor. If I am not laying into it I can get 18 mpg but I enjoy the TRD dual exhaust sound too much. Anyway, glad to see they have come a long way. My previous truck was a 2003 GMC Sierra 6.0L in the 1500 and it got 11 mpg city and 13 highway. It was horrific but I loved that truck. I kept it until 2021 when I bought my TRD Pro Tundra. Hope you get to keep your GMC a long time too and enjoy it for what it is!

[@AdventureRocks]

Thank you, appreciate the comment

[@tonyseets]

Great video! At ~2200mi currently on my ‘24 Silverado midnight edition with the L8T and factory MTs. Haven’t yet seen over 15mpg but also hadn’t really planned too. Have left Trip 2 untouched since I drove it home (~400mi) and that’s currently sitting at 11.2mpg yeehaw 🤠💸

[@AdventureRocks]

Thank you. That midnight edition is SHARP! Honestly I'm thrilled with the 16.6mpg...so even if it never gets better I'm completely satisfied considering all things.

[@CTECH-REVIEW]

Loving the videos man! you have done much better that I did when doing mpg loops with the L8T. That motor is so solid I love it. 16.6mpg at 65mph is excellent with a gas HD truck.

[@AdventureRocks]

Thank you! Glad to hear. I am really enjoying the truck as well.

[@ericmackison9517]

My 17 Silverado had the dead pedal and my 19 RAM doesn't and i honestly miss it. One thing nobody talks about in thr RAM HDs is the massive center hump on the passenger side that protrudes into foot room that other trucks do not.

[@AdventureRocks]

Great point. Thank you for sharing.

[@bradniehues9560]

I’m averaging about 14.5 on the highway with my 24 AT4. I had a 23 with the 6 speed and it got a little better, but not much better. My 23 was an SLE with 18” tires. The AT4 weighs about 350 lbs more and has 20” tires. I have 10K on it now. I wish it was a little better but it does tow better than my 23. The 10 speed is a great transmission. Maybe it will get better with time, but I”m a believer they get what they get and don’t change a whole lot.

[@AdventureRocks]

Thank you for sharing. I love the AT4...super sharp truck. I got the oem 20" wheel upgrade with all-terrains on mine, but sometime I'll have to check the overall dims if they are different or just a narrower profile tire. I'm very pleased with the MPG given how tall it sits and heavy it is. Bet your 24 is a sharp looking truck though, inside and out.

[@powercamper0]

Hi I have a 2021 1 ton with the 6.6 gas engine and 6 speed trans. We live in NH. quite hilly here. If I'm on flat going it does good about 16.0. But if I'm pulling hills it cuts down quite a bit. We went to NC. last summer and got 9.5 pulling the 30 ft. camper.

[@AdventureRocks]

Thank you for sharing.

[@sam-68-56]

Great update and my mileage was almost identical same conditions, same truck with a little over 1K miles. Will be doing first oil & filter at 1500mi. Should be better mileage after broken in. I will do all the other fluids at about 25K, except coolant. Will wait awhile on that. Keep up the good videos and updates!!!

[@AdventureRocks]

Thank you! Great points.

[@chriscampbell8648]

I have a 2022 Chevy gasser 2500 2wd. I rarely get to do a road trip without towing something but about a year ago I had to drive from coastal MS to Gainsville, FL to pick up a boat. I had nothing behind me on the way there, ran about 70-72 mph and got 16.8 mpg. On the way back, I was towing a small boat, motor, trailer (14.5 footer/15 hp) and I ran 65 mph and got 16.5 mpg. IMO, this is pretty good for a large, heavy truck.

[@AdventureRocks]

Thank you for sharing. Agreed very good and pleased with the MPG I'm seeing. I'll release the towing MPG this weekend.

[@PineMountain981]

That is excellent.

[@JeannyCollazo]

Nice video. Totally agree many do not get HD trucks for fuel economy but is important to know what to expect at the pump. It blows my mind HD trucks are not required to display MPGs on the window sticker.

[@AdventureRocks]

Thank you. I am still thrilled with the 16.6mpg and truck overall. I'll release 1st tow this coming Sunday with initial impressions and towing mpg.

[@joethomas6457]

Chat town. Use to live there. Florida now. My 24 HD duramax is in dealer for a new 10speed at 9k. Its a standard cab if that matters. I get 24mpg at 62 empty. Got 17 with small enclosed 6-7k at 75mph. My 5.3 half ton gets 12-13 on highway with same trailer.

[@AdventureRocks]

Thank you for sharing.

[@PineMountain981]

Is yours a diesel or gas engine?

[@toddanderson8277]

First of all, your truck is beautiful, and I am on my second GMC Sierra 1/2 ton with the 5.3. We are RVers and my first was the 2000 5.3 and now a 2015 5.3 both with the 3.73 and max trailering options. I am following your videos as I am always thinking of my next truck down the road and if I were to get a different rig, I think I would go with the 6.6 gasser. I wouldn't be pulling anything over 12,000 pounds and only a weekend warrior as some call us besides the longer summer trips, but it isn't justified to spend the extra money for a diesel for what we do. Looking forward to seeing your new trailer and hearing how the truck performs towing and etc. Thank you and keep on trucking.

[@AdventureRocks]

Thank you! I am really enjoying the truck. Just pleased overall with everything and how it's performing.

[@kirkdunn1379]

all my trucks been really close to the same.... and all 6spds My best was a run from Burbank to Long Beach in so cal and reached 21mpg a few times, I do this run quite a bit.... going up its about 17-18

[@tonyread5559]

Better than my 1st gen Tundra and my dad's 2007 Duramax. The whole time I was thinking, that looks like TN. Then I saw your map and confirmed it.

[@AdventureRocks]

Sharp eye for geography!

[@Jbennyho]

Great review.

[@AdventureRocks]

Thank you, appreciate the feedback.

[@nickfountain8420]

16.6 mpg is not too bad for a small block in that big heavy truck. I’m hoping you put out some reliability/quality videos in September or October just before GM starts offering some better incentives for the outgoing ‘24 model years. I’m strongly considering this as my next truck even though my ‘16 1/2 ton Silverado has had all sorts of issues. Paint peeling, A/C compressor replaced, and I made the 8speed last until 181k before I had to replace it. It started showing problems at 130k, but I managed with its issues for 51k more miles. Just now getting an AFM lifter tick. Although I’ve had that system tuned out since the truck had about 15k on it. Wish I would’ve gone ahead and mechanically blocked it off also.

[@AdventureRocks]

Agreed, thank you for sharing. I've been very pleased with the 6.6 + 10sp, especially towing. Will post 1st tow this weekend coming up. I'll plan to share full ownership experience and publish more in future...the good, bad, ugly, etc. A lot to like on this one though.

[@nickfountain8420]

@@AdventureRocks Looking forward to it. Only reason I'll consider another GM is due to the 6.6 gas motor not having AFM. Cylinder deactivation on any vehicle is absolute garbage.

[@AdventureRocks]

@@nickfountain8420 Great point, one less thing to go wrong.

[@nickfountain8420]

@@AdventureRocks If you're planning on keeping the truck a long time, google catch can or pull up a video about a catch can. You'll probably want one on that truck since it is still direct injected and there is no fuel from port injection running over the back of the valves. Should save you from having to worry about the valves getting excessive carbon buildup on them for a good bit longer is the idea behind a catch can anyway.

[@AdventureRocks]

@@nickfountain8420 Will do, thank you for the tip.

[@Podchynok]

My 2021 6.6 gaser took about 10000km to 15000km before I noticed improvement in mpg.

[@AdventureRocks]

Great tip, thank you

[@socaljarhead7670]

What’s that in American?😉

[@Podchynok]

@@socaljarhead7670 6500 to 9500 miles

[@sargeatlarge24v]

@@socaljarhead76705-7500 miles. Usually it’s about half. It’s funny when they try to flex million kilometers like it’s something special when it’s like 460,000 miles

[@ArtbyLordTV]

Dang gas truck is getting better than I do in my duramax…

[@AdventureRocks]

I hear you...it surprised me too. I've been so pleased with the gas L8T overall. I'm getting about 13mpg mixed daily driving, and typically 16-17mpg highway unladen. If I go faster over 70mph then it'll go down naturally.

[@jimgreeves7928]

What is the gear ratio of your truck? My 2017 2500HD with the gas 6.0 has 4:10 and I get 5 to 6 mpg towing our travel trailer

[@AdventureRocks]

I hear you. Mine is 3.73 with the 10sp. I think GM only offers the 3.73 on the 2024s. I was surprised with the high 9s for towing mpg. I was not expecting that as like you my last gas truck always did 6ish towing. I think the 10sp really helps towing.

[@T3Garage]

Shoutout to Chattanooga! 👏

[@AdventureRocks]

Indeed! Beautiful country and drive.

[@mikehrynyk434]

Head wind, side wind, tail wind……there you go

[@ham-truck-fishing]

Wow that's right in line with my 22 6 speed 6.6 gas.

[@samuelbranson6138]

Outside temperature also makes a difference . I think that might sounds good.

[@AdventureRocks]

Great point. Thank you.

[@jaimemartinez7016]

Thx for the info , what tire pressure are you running ?

[@AdventureRocks]

Just slightly over OEM recs, 65 & 72.

[@chadmiller6487]

I have a 23' GMC 3500 DRW with the 6.6 gas. I have 45k miles on it. I average 15mpg unloaded and 9-10 mpg towing.

[@AdventureRocks]

Thank you for sharing. I bet you've got a killer payload on that truck!

[@chadmiller6487]

@@AdventureRocks 6500lb

[@AdventureRocks]

@@chadmiller6487 Wow!!! That's awesome!

[@MAJORMAN299]

10 speed allison???

[@chadmiller6487]

@@MAJORMAN299 no. 6 speed.

[@mkbmj]

Can you do your next run with 93 octane? Every vehicle I’ve ever owned has gotten 1-3 mpg more with Shell 93

[@AdventureRocks]

Great question. I've been contemplating doing a future run with higher octane to see if any difference. A lot of opinions on both sides, but would be interesting to see real world results and determine if the increased cost of the 93 octane delivers a satisfying MPG result. Very interesting experiment...

[@dylanluhowy]

My 2023’s lifetime average is 11.8 MPG. I typically get about 16 MPG (14.5 L/100km) on the highway at 65 mph. Towing a 10,000-lb fifth wheel gets about 8 MPG.

[@AdventureRocks]

💪🏻

[@davidhouchens4998]

I turn my battery disconnect off to stop the solar panel from feeding back to the truck.. had same issue.

[@marcaliventialiventi765]

I have a 2018silverado. Without the camper on the highway best milage was 31 to the gallon. You have to plan trips that go through at least two tanks of gas the milage improves

[@jerry-381]

Sorry if I missed this but what size wheels/tires do you have on your GMC?

[@AdventureRocks]

Sure, no problem. They are overall about 33" diameter and the size is LT275 60 R20. They are the "all terrain" OEM tires from Goodyear = Trailrunners. Here's a clip at relevant timecode if interested in further details: kzbin.info/www/bejne/qmjVdatmh9F9Z68si=I9QtIg2CBZrd3Z8G&t=946

[@jerry-381]

@@AdventureRocks thanks! I’m looking at Chevy for my next truck and actually don’t want the 20” wheels. I’m looking at the LT trim and it’s hard to find that trim with 18” wheels in my area.

[@AdventureRocks]

@@jerry-381 I hear you. I vaguely remember someone commenting at some point on the overall size of the 18-in combo, and I think it was a taller sidewall and maybe almost as tall overall compared to the 20-in combo, but my memory is fading on the specifics.

[@jerry-381]

@@AdventureRocks interesting I looked it up and you’re right the 18” tires are 275/70/18 which is actually 33-1/2”. I never realized that. Thanks for the info🍻

[@coozhunter4434]

The 18 inchers get better mileage than the 20's. Unsprung weight being so important...... I've tested both

[@ridingwithrusso7790]

Could winter fuel be hurting the MPG?

[@AdventureRocks]

Great question. I'm not sure, certainly possible with temps. But, I gotta say I'm thrilled with the 16.6mpg either way.

[@bruceblackerby3742]

Have a 2024 3500HD PRO with the flexfuel option. Got about 15 mpg on first tank of 87 octane. Get about 13.5 on E15, and 12 on E85. Get yourself an oil catch can system if you haven't already. Surprising how much oil gets recirculated by the pcv system.

[@AdventureRocks]

Thank you for the tip.

[@lexuslowlife3055]

I would like to see how that truck does in south Florida at sea level in the flat part of the state and also because the speeds here are a lot higher. On open highways between big cities the left lane is at 85mph and middle lanes are at 80mph to see how the truck does. I have a 24 Duramax with 3k miles did my first oil change at 1k miles and I’m doing 17.6-18.3 currently at 80mph and also temperature makes a big difference in 50° weather it’s drop about 1-2 mpg when in 70° and up it’s doing closer to 18mpg at 80mph

[@AdventureRocks]

Great points! Agreed, I'd like to see the difference it'd make. Surely it could only improve on the L8T.

[@lexuslowlife3055]

@@AdventureRocks new to channel great videos man keep them coming and congratulations on the new truck.

[@AdventureRocks]

Thank you @@lexuslowlife3055

[@dmc9791]

my 2010 2500 6.0 L mileage is 12.5 and towing 7500 LB camper at 55mph is 10ish if i would drive 65mph it would be 8mph so I wish I had the .66L for more power and torque

[@AdventureRocks]

I hear you. I'll be releasing the 1st tow video on Sunday. I am really pleased with the 6.6L and 10sp. I like it A LOT.

[@chris-vd8tw]

Your truck gets better mileage then my Tundra

[@AdventureRocks]

Wow! I'm very pleased with it. I average closer to 13mpg mixed country driving, unladen.

[@chris-vd8tw]

@@AdventureRocks ya word. I actually test drove a 24 GMC HD today and was very impressed with it. Im very close to making my decision of buying it. Awesome trucks

[@fivesfilms]

What made you choose the Chevy 6.6 gas over the Ram 6.4 hemi?

[@AdventureRocks]

I'll try to do video in future explaining more in-depth, but mainly the dated platform and smaller cab/bed on RAM swayed me toward GM.

[@fivesfilms]

@@AdventureRocks I can agree with that, but for whatever reason I still like how the Ram looks and it's interior and the fact that the fog light swivel direction when you turn. This Duramax drives way more refined than the Ram.

[@AdventureRocks]

@@fivesfilms great point. It's a tough decision for sure.

[@JackDrenalin]

Nice video. Have you experienced any oil consumption issues. The GM BULLITEN says you can expect 1 quart of oil consumption between oolmshsnes.

[@AdventureRocks]

Thank you. Great question. No oil consumption issues yet. I'm keeping a close eye though as I've heard the buzz about it all. Thanks for the reminder.

[@kirkdunn1379]

had 3 of these and not one burned oil

[@CLY0556]

Were you in eco mode?

[@AdventureRocks]

No ECO mode on my 2500 HD with L8T, just normal, tow/haul, and off-road

[@theocdhub822]

Would you be interested in reviewing on of our products on ur truck?

[@AdventureRocks]

I can check and determine if we're a good fit. What kinda products do you make/sell?

[@theocdhub822]

@@AdventureRocks we sell PPF screen protectors for infotainment system and we also offer gloss black PPF pillar kits for the excessive scratches and swirls on the doors.

[@AdventureRocks]

@@theocdhub822 I can check them out and see. Are you on Amazon or where do you sell?

[@randysaunders4247]

Would it make any difference using a higher octane gas , like 89 or 93. I think you were using 87 octane.

[@chrism8013]

Octane rating is due to the compression ratio of the gas to expel it's energy upon detonation. The higher the compression ratio that the engine is tuned to, the higher octane of gas is needed. Higher octane in a lower tuned engine, actually costs more money. Therefore decreasing MPG.

[@randysaunders4247]

So those trucks are tuned for lower octane. Thx for info.@@chrism8013

[@AdventureRocks]

Great question. I've often contemplated doing an experiment to confirm results...maybe one day? I kinda think the cost difference to use higher octane may outweigh any improvements in fuel economy gained, but it'd still be interesting to confirm in real world. You are correct about the 87 octane though. Thansk for sharing, great comment.

[@jesuscastro687]

I use premium 91 on 2020 hd 6.6 denali only 30k miles... I should use 87 ? Full tank 498 miles

[@jerrodpatterson8938]

What ram had over 1000 foot pounds of torque? The new ram diesel only makes like 850. None are over 1000 now besides Ford.

[@kennethobando5755]

Ram is confusing. They have two power levels on the cummins. Standard power model and then a high output model which has way more horsepower and torque(well over 1000lb ft of torque) . But the majority of them sold have only 850 lb ft.

[@AdventureRocks]

Correct, it is indeed confusing. The HO 6.7 Cummins was in my 21 dually at 1075 lb feet of torque...you could really feel it when towing heavy too...kinda like a rocket thrusting you forward. I had special ordered it to be a towing beast witht he 4.10 and Aisin trans. Great truck if you need to tow heavy.

[@Icutmetal]

Incorrect about the HO Rams.

[@Backyard_KLX]

Very close mpg to my 2023 turbomax 1500

[@rogern5368]

???? Of topic but do you push the button to shutdown the auto stop start every time you get in ??? I hate the idea and was doing so every time it’s hotter than h ** l here and I don’t want to let it tell me when it will shut down. !! I did install a great product to eliminate any need to push a button every time I start my truck to drive. Love that truck of yours. Yukon XL 2023 4X4 SLT 5.3 sterling metallic !!

[@AdventureRocks]

Thank you! Great question. I do not have the auto start/stop feature on my 2500 HD. I could be mistaken, but I don't think it's available on the HD trucks.

[@kirkdunn1379]

there isnt any on HD trucks

[@biglug9364]

I do not believe that waiting to top off a gas vehicle after the pump stops applies as diesel phones and it takes a few seconds for the foaming to die down I do not believe gas does such

[@chrism8013]

I own a '21 sierra 1500 with the 6.2L & I understand the weight & height difference between both yours and mine, but my 6.2L has bested 26.5 MPG on the hwy so far. I'm really surprised the 6.6L is that much lower.

[@AdventureRocks]

Agreed that's a big difference, especially comparing the displacement

[@ab6777OG]

The 6.2 is designed as a passenger car/ light duty engine and made to be efficient. A good engine, but apples and oranges.

[@chrism8013]

@@ab6777OG The 6.2 has 420 HP & 460lb-ft of torque. That's definitely not light duty. The new 3.0 LZ0 diesel is rated for the same torque of 460. The 6.6 is rated 401 HP and 464lb-ft of torque.

[@vegastyle84]

26mpg doesn’t seem possible…

[@chrism8013]

@@vegastyle84 May not seem, but it's true. If I could take a pic of my dash and post it here, I would.

[@billylord7311]

WTF?!! I get 15mpg in my 2024 2500 with the duramax!

[@AdventureRocks]

I've been very pleased with the L8T so far.