Thanks for the replies everyone. I know my tires probably arent helping me at all. It has 315-75-16's on it. It also has a 6" rough country lift. Its a pretty tall truck.

I have a 2000 Ford Powerstroke diesel. Its the 7.3L. Its getting horrible fuel mileage for some reason. Only 10mpg. I dont exactly drive like a 100 year old man but I dont just mash the pedal to the floor all of the time either. I always try and keep it under 3000 rpm. (It redlines at 3200...Ive...