I have a 2001- 7.3 PSD, F-350, DRW, 4x4, Crew Cab with 4.10 gears. This truck is box stock. Best mileage Iíve ever gotten is 15 in the NC Mountains. I get 12 mpg on the highway at 75 to 80 mph and 12 around town. With a 41í (#16,500) or a 36í (#10,500) in back I get 9. These are real numbers in level So. Florida, not overhead computer numbers.