Powerstroke VS V-10
I do not mean to argue with you but... You are apparently a Ford fan to the core. I actually own 2 duramax trucks. An '03 Chev and '04 GMC both 2500HD's. I own an RV dealership and pull trailers of all types all the time. Yes, both trucks will get 20 mpg on the interstate. I do check my mileage each and every fillup. Locally and towing, I do get the mileage I stated.
You are correct in your statement that V10's are used a LOT in motorhomes. Guess what, they seem get better gas mileage in them than they do in pickups. I do not know why, just what I have observed. The 4 MPG was no lie, we watch the gas needle moving. It was in a 2001 SB Cab/chassis with a flat body on it. I was very glad I was just borrowing it.
I have owned three F-350's in the past. I have been in business since 1985 and have had LOTS of trucks. The three Fords, as a whole, were the worst of the bunch. I will admit that one of the 3 was a fairly good one until it got some miles on it. One of Fords was on its 5th clutch at 60K and the transmission had been rebuilt at 23K. Turbos had to be replaced on all three and we were plagued with exhaust leaks. NO, we do not abuse our equipment. When the 5th gear shattered, we were towing 6,000lb. I will actually say that the two best trucks I have had were both Dodges. Sorry, you probably don't like what I am saying but that is why there there are several truck manufactures. In my opionion, thank goodness.