I recently purchased a used, yes used, '08 F-350 SD, CC, 6.4L Auto, 3.73. The original owner had it for 2 months and put 1800 miles on it. So I called him and asked him why he got rid of it and he said he was a Chevy guy and tried the Ford, but had to go back to a Chevy. This made sense as I bought it from a local Chevy dealer.
Anyway, I have been getting somewhere around 11-12 mpg doing mostly interstate driving. I recently took it on a 500 mile trip and even then could not pull 13. Now I drive somewhere between 75-80 on the interstate with the CC set.
The truck runs great. It does not seem to be stuck in regeneration and the power is smooth with no hickups, so I am guessing I don't have the injector issues, (Truck hit the selling dealer in 4/07, but not sold until 9/07).
So I was wondering a couple of things. Should I be getting better mileage and what RPM's are you all seeing at say 70 MPH on a flat road? At first I thought it might have the 4.10 gear, but I got the selling dealer to order me a window sticker and it has the 3.73.
Thanks for the input.