[shakenfake]

Are you running 93? @RDF1

 

[RDF1]

Are you running 93? @RDF1

I run the cheapest 87 i can find right now. Once i get my engine done ill have to rethink it. Probably start out on 87 just to have a fall back tune to revert to if need be.

 

[candiazoo]

Yes, I'd also stick with my 1500 for towing that daily.
Mileage will depend on if there a lot of stops/starts , speed changes, how fast it will be travelling and the aero load created by the trailer.

But it isn't only about the mileage. It is also about stability and the 2500's are heavier with a stiffer suspension, helps in highway situations with trucks blowing by you and high winds. I could be wrong though.

 

[RDF1]

I agree.. Ive towed a bunch with my 1500 and my 2500HD is much more stable with heavier loads.

 

[yepih1]

Same for mine, truck and engine are great, I average around 18 mpg until I tow something then drops lie you say depending on load, Mine is mostly country miles not much city driving, seats suck all are made for a person under 5'5 tall, feels like its trying to bend my back like a hunch back,

 

[silverdave]

Hi,
How is your experience with L8T sierra engine?
1. How is reliability?
2. MPG? Avg mpg? Hwy mpg ?
3. Do you experience high oil consumption per 6k miles, even when not towing?
4. Any issues with knock sensor?
5. Do you believe L8T can last 200k miles without major breakdown/repair? Of course assuming one is taking care of service intervals etc.

Deciding whether L5P or L8T.
L5P seems to be great but those regens...
Thanks !
Bob

I have a '24 Silverado CC, LT Z71 with the 6'10" bed. It has the L8T, and I don't regret this decision one bit. Like you suggested, the diesel is just too maintenance-prone, assuming you don't actually need to carry super heavy loads, and/or tow in very high elevations. I tow no greater than 12,500 lbs, and it handles the load very well (the tow rating is 18,400). One major advantage of getting a gasser is payload; mine has a 3,553 lb payload rating.

I don't have any of the issues that you listed, not one. This engine is specifically (over)built for the long haul. My only real concern was oil consumption, but after four oil changes the dip stick shows the same level before and after changing it (I go no further than 5k between changes).

Since you posted this quite a while ago, I'll assume you already made a decision, but this may be helpful for someone else.

 

[silverdave]

I have a '24 Silverado CC, LT Z71 with the 6'10" bed. It has the L8T, and I don't regret this decision one bit. Like you suggested, the diesel is just too maintenance-prone, assuming you don't actually need to carry super heavy loads, and/or tow in very high elevations. I tow no greater than 12,500 lbs, and it handles the load very well (the tow rating is 18,400). One major advantage of getting a gasser is payload; mine has a 3,553 lb payload rating.

I don't have any of the issues that you listed, not one. This engine is specifically (over)built for the long haul. My only real concern was oil consumption, but after four oil changes the dip stick shows the same level before and after changing it (I go no further than 5k between changes).

Since you posted this quite a while ago, I'll assume you already made a decision, but this may be helpful for someone else.

Oh, and the fuel economy isn't wonderful but it is tolerable. My best 25 mile duration is 23.5 (according to the computer), which is a fluke. I was going 65 on a flat road in Florida in one of the cooler months. I typically get 18-ish (maybe 19) at that speed. Towing 10k at 62 mph takes it to around 10-11.

 

[Mudhog]

2020 6.6 with 83,000. I averaged 12.2 mpg pulling a tandem axled 12' u-haul trailer loaded to the max from south Texas to Raleigh North Carolina 1600 miles. Coming home empty with Cruise on I averaged 17.2. At one time I was averaging 18.5 until I hit the big hills. No oil consumption yet, I change it at around 5000 mile no matter what the meter says. It has never been low on the stick. My average after 3200 miles was 14.2 with half of that pulling the trailer, and 3 days running around downtown Raleigh then home.

 

[PaleRider]

Im loving my '25 6.6. CCSB/4x4.

I average about 12 mpgs. I do not drive with efficiency in mind.

No clue on consumption. Im 6k miles in and already 2xoil changes done haha

 

[ajaquez2991]

Hello everyone, I just purchased my l8t leaving the 2017 l5p behind hard hard decision it was. I saw a lot of people claiming 18 mpg 9 mpg towing. I thought that was amazing for a gassed HD. I bought a 2025 custom for the middle console fold up 😎.
Im at 1200 miles i drive 130 miles a day round trip. I have not seen better than 15 -16 mpg im consistent with 70mph ive done the 80mph test no trailer 14-15mpg, city driving it drops to 9, could this be cause the engine break in is happening? Ive also done 91 octane I feel like it felt a difference in response but not mpgs. So idk how I feel just yet maybe the extra gas tank kinda pays for the extra maintenance on a diesel. We'll see as time comes. Besides mpgs I love it. And im interested how other owners feel about theirs as well.

 

[PaleRider]

I have never seen an 18mpg claim on the 6.6 gas, I would suspect they intended to reference diesel.

My truck reports a highest isntant reading of 18.1 and a long term average of 13.4 over 6k miles.

 

[PaleRider]

I was a little off on my average hahaha

 

[lineman1234]

I get,,, with summer fuel at best, 17 per tank non interstate travels, winter hear it gets cold and with winter fuel my mpg's drop 1-2.
Going 82 on an 80mph highway with a headwind, its nothing to brag about for fuel economy, but gets the job done just fine, empty, towing the 5ver or the truck camper on it. No, i dont do 80 with the 5ver, but yes with the tc.

In the pickups i have had, it seems 2mpg higher 2wd vs 4wd, so those in,,, lets say florida, or other areas that dont need or someone that doesnt want 4x4, will get better fuel economy.
So i could see 18 or a touch more with a 2wd.

I know when i found and ran 2 full tanks through, of non ethanol fuel just normal 87, it gained 1.5-2mpg solid, tank to tank. Mine is a 4x4 regular cab 2024 3500 gasser.

 

[tooleyondeck]

2025 HD L8T CCSB:
1. Solid thus far
2. 11-12 city, around 14 hwy, best was 17mpg on a long 55mph stretch
3. Just hit 6K but no consumption issues yet
4. No, didn't know that was an issue with any Gen V engine
5. Absolutely, with no DFM and proper maintenance

 

[gofast2001]

I have a 2020 2500hd, with 82000 miles. I get a solid 16.5 at 75 mph on 87 ethanol. I tow 11,000 lbs travel trailer. At 65 MPH, I get between 7.5 and 10 mpg. At 6500 miles I add I qt mobile1.The l8t is a very strong puller. Very happy.

 

[JRinReno]

Im loving my '25 6.6. CCSB/4x4.

I average about 12 mpgs. I do not drive with efficiency in mind.

No clue on consumption. Im 6k miles in and already 2xoil changes done haha

What gears do you have? I am giving thought to selling my '14 K3500 6.0, AT with only 42K miles on it and buying a'26 like your truck. The '14 runs so good that I hate to get rid of it. I had a custom tune done with HP Tuners software and it really helped. BYW, it has 3.73 gears.
Prior to this truck I had a Ram 3500 CCSB/4x4 with a Cummins, mileage went WAY down when I towed anything.

 

[PaleRider]

What gears do you have? I am giving thought to selling my '14 K3500 6.0, AT with only 42K miles on it and buying a'26 like your truck. The '14 runs so good that I hate to get rid of it. I had a custom tune done with HP Tuners software and it really helped. BYW, it has 3.73 gears.
Prior to this truck I had a Ram 3500 CCSB/4x4 with a Cummins, mileage went WAY down when I towed anything.

Im running OE gearing.
Gas is 3.73
Diesel is 3.42

No plans to change it either.