I have a 2011 4×4 2500 LTZ Crew Cab that I lifted 3 inches to run 14×35 tires on it , installed Rhino bumpers, line bored the exhaust to run a 4 inch straight pipe ,took out the EGR pipe, cold air intake and we installed a programmable 5 position chip box in it. Has so much power in stock mode I can smoke the tires ,beat many performance cars in a race ,pull a 38 ft Donzi on its trailer Or a loaded semi pretty fast
It has 215,000 miles on it , I drive it daily average in town & interstate which averages 16.4mpg, on the interstate at 70 mph I get 18-19 mpg or towing a 15000lb boat get 12-13 mpg
We did the same to my buddies truck that is stock and he gets 10 mpg more than I do

K&N air filter helped my 2018 pick up 1to 1 1/2 mpg.

I put Michelin LTX tires on my 2018 Duramax and get 23-24 MPG running 65. That’s an increase of 4-5 MPG over the stock Goodyears that came on it. Tire pressure plays a big role along with not flying out of the hole and not passing other vehicles. I run 70 lbs in the front and 75 in the rear tires.

I have a 2021 chevy 3500hd dually long bed and my average mileage is also 14.5 with no load. That is running at 75 mph. I have gotten better mileage at 65 mph (around 17) but driving at that speed unloaded doesn’t work for me. I have a 16k 5th wheel that I have not towed yet so it will be interesting to see how that works out. In 50 mile average I have gotten as high as 21.6.
Jim

I have a twin to your truck. Mine is pure stock everything. How do you achieve the mpg’s you mentioned? Pulling a large load I get 10.5 or so, empty I get 14.9.

How about towing milage. My 09 gmc duramax 4dr long box with a tuner and bigger exhaust gets 22-24 mpg at 60 mph 20-22 mpg at 70 unloaded and 18-20 mpg at 80 mph. Towing up to 10k lbs i got 12-14 mpg between 60 and 80 mph. Hauling 15k lbs of hay bumper pull i averaged 10-12 mpg doing 60-70 mph. 209k miles on it now. My mother had it with bully dog system on it from about 100k -163/169k miles which is when I bought it from her. I pulled a 76 k20 long box reg cab loaded with furniture in both truck boxes from nd to Michigan got 16-17 mpg.

Is your truck a Dooley I’m fixing to purchase two of them to start pulling campers for hire was kind of curious about what type of fuel mileage they would get

Thanks for an honest statement of MPG. I can’t believe that anybody is getting 14 MPG plus pulling a travel trailer