Not the same but here is my experiance. I had a Sightseer 26p with 8.1 chevy with Banks upgrades and now have a Tiffin Red 38QRA with 6.7 Cummins. The Sightseer was a16k chassis unsure of actual weight and Tiffin is 29,500 chassis and weighs 29k. I pull a 20ft enclosed trailer with side by side and motorcycles in it. The 8.1 went 45mph up Donner and got as low as 4mpg on one trip in wind and as high as 8mpg. The 6.7 averages 7-8mpg all the time and goes 45mph up Donner pulling the same trailer. The Tiffin drives nicer and is much quieter.