We were on our way back from the race track(Thunder Road Vt) after my son`s race. I drive an 2004 FX4 F250SD Crewcab V10. There was a good size hill on interstate 89 north and I looked in my mirror to see a Chevy thinking he was going by. We let him get about half way by( we have a 24ft enclosed he had a 20ft enclosed)I could here the Duramax growling, then I rolled on the gas to start to pull away when I noticed the smoke cloud. I figure he was chipped up and had a big exhaust hanging there. The more smoke poured out from him the further back he went. We pulled away like he was tied there. We had the same thing happen a few weeks later with a Dodge, except the Dodge was trailer-less. We left him up hill and on the flats too. To some it up I think the V10 is the best gas engine for the Super Duty. The way I see it if your worried about gas mileage you shouldn’t be driving a truck anyways. The only thing I would change is making it with an optional supercharger.This truck will pull anything. I have been driving Fords now for 20yrs. And still own my first Ford its an 1981 Mustang.