2022 Chevrolet HD Duramax

[lbnaz]

Does anyone have a new HD Duramax to compare fuel mileage with. I purchased a new one a 3500 srw longbox 4x4 High Country and the fuel mileage has only been 10.9 to 11.6 in town driving. I'm still breaking it in so I haven't pulled a 5th wheel yet to see what that brings. I've got 900 miles on it and still the same mileage. Had it checked for any codes or software updates there are non currently.
I know you don't buy these trucks for economy but I traded in a 2020 same truck and it got 18-19 city average (best was 21) and it got 12.9 to 13.5 pulling a loaded 5th wheel. To many other electrical and mechanical problems with it to keep it. Now I'm missing it. Thanks, Larry