GMC purchase mileage question

Papsqueeg

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Looking to trade in my 2020 GMC sierra 1500 withn5.3 and 6 speed tranny and 373 rear end getting 14 mpg avg on a daily driver. Want to buy a GMC sierra 2500 with 6.6 turbo diesel 10 speed allison and a 3.43 rear end. So the question being asked is what kind of milaege should the 2500 be averaging on highway and city driving. I occasionlly tow a 16'x7'x7'h trailer for hunting and a 6x12 every weekend to camp with atv and mower. Also it is a work truck driving 40+miles daily round trip will be hauling necessary tools as i install mostly kitchens do not haul or pick up cabinets. Thanks in advance.Dan
 
Not same truck but would expect simular numbers. My Ram gets 13/14mpg towing simular trailer, 18ish as daily driver and 20ish under ideal highway circumstances (based on installed lie-o-meter). The real difference isn't mileage it's how it pulls/stops trailers. Good luck
 
3500 Silverado diesel for work averaging over 14, mostly highway, towing UTV more than half the time.
 
I have a 2020 chevy 3500 diesel. I get 14-16 daily with no load but i live in the mountains. Flatland it gets 16 city, up to 20 hwy unloaded. Towing in the mtns Im at 10-11 mpg with a 8000lb load, flatland maybe 12-13. Mileage doesnt change with a ton in the bed, just rides better.

Hugely dependent on driving speed and style. Slower, as in 65mph vs 70-80mph, and slow acceleration, will increase mpg 1-2 instantly.

Or kick on the banks module to level 4 and the truck turns into a 10,000lb rocket ship 😏

Miss my ram 2500 cummins but the allison trans is far superior vs the 68rfe. Independent front susp is better on the road too for chevy vs straight axle ram which did better off road.

IF you get a chevy or gmc diesel, get the banks upgrades - intake, mass airflow sensor piece, and monitor module (may void warranty though). Also dont top off DEF, let it get low before refill, functions better for some reason.
 
I have a 2021 GMC Denali with a diesel. I average 18-19 when not towing. It’s an all time fav vehicle for me.
 
Look at the baby duramax.
My son bought a 2024 GMC AT4 with the 3.0 Duramax and 10sp trans. We just moved him from Arizona to Montana about a month ago. He had a large gunsafe in the bad and towed a two atv's on a trailer. He got 24mpg over 1000 miles at 75mph.
 
13-15 around town 15-18 highway, better with a following wind or headed east out of the mountains.

2023 2500HD Sierra AT46.6 diesel…16mpg 500 miles from North Central TX to Santa Fe today into a stiff headwind. Power out the kazoo.

I will probably get 1500 small Duramax next cycle.
 
Last edited:
Huh - So I should be happy with my 19-22 daily in my 2017 1500 Sierra. 6 speed tranny and 3.43 diff.
Just came back from Nevada trip and Last 400 on info center says 23+. Don't be asking me to actually read the odometer and pump and to math.
Had zero payload. Just a couple rifles and a cooler.
 
Looking to trade in my 2020 GMC sierra 1500 withn5.3 and 6 speed tranny and 373 rear end getting 14 mpg avg on a daily driver. Want to buy a GMC sierra 2500 with 6.6 turbo diesel 10 speed allison and a 3.43 rear end. So the question being asked is what kind of milaege should the 2500 be averaging on highway and city driving. I occasionlly tow a 16'x7'x7'h trailer for hunting and a 6x12 every weekend to camp with atv and mower. Also it is a work truck driving 40+miles daily round trip will be hauling necessary tools as i install mostly kitchens do not haul or pick up cabinets. Thanks in advance.Dan
I have a 2021 GMC 1500 with the Elevation package. Crew cab with 3.0 diesel which now has 60,000 miles and I love it. It easily pulls my 14 foot tandem trailer with my Honda Pioneer 1000 and unloaded I get a no bull 27-28 miles per gallon (over a 50 mile average). My best is 36 miles to the gallon but I was feathering it just to see what I could do on my way to work which is 43 miles one way. The newer models have even more torque. Turn it to sport mode and this truck will haul the mail.

No regrets with this truck.

Mark
 
I have the 2018 GMC 2500 with 6.6 and have loved this vehicle. Best thing I have ever owned. It currently has 124,000 miles and has essentially gotten 17-20 around town and best I have ever gotten was 23 coming back from RMNP and coming across Kansas. Wind was at my back and cruise was set. It has recently gotten an "enhancement" and my gas mileage has increased drastically on my last trip from NM back to NC.
 
Huh - So I should be happy with my 19-22 daily in my 2017 1500 Sierra. 6 speed tranny and 3.43 diff.
Just came back from Nevada trip and Last 400 on info center says 23+. Don't be asking me to actually read the odometer and pump and to math.
Had zero payload. Just a couple rifles and a cooler.
Bad form to reply to your own post. I'm correcting myself. Jump in the rig yesterday and the info center said 19.5mpg
 
Bought a 2024 GMC 1500 Heavy half with the baby Duramax. Pulls a 21’ Jayco camp trailer like it isn’t there. Gets 12-14 mpg towing @ 70 mph. 24-28 mpg around town. 24 mpg on the highway @ 80. Absolutely sold on it!
 
@Raisin Bran Whats your GVWR? Is your truck a ccsb or cclb? Single cab?

Im curious because I dont NEED a ccsb 3500, and would love the mpg the 1500 baby duramax gets when not towing. When I spec'd out a new 1500 the gvwr was too low. I tow a 30' travel trailer with a 8800lb gvwr. Sometimes I load the bed up heavy too but I mainly need to be able to pull 10k.
 
Kinda surprising that your 1500 is only getting 14mpg (unless of course it has big tires, lift, you drive like a nut, etc). I had a 2009 that averaged about 18 with the 4 speed tranny. I bet the 2500 diesel averages better than 14 and will tow more efficiently.
 

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