Mileage went from 12 mpg with bed to 10 as you see it now. I wish the mileage was better but what do you expect from a full sized truck and a 460. I go back and forth on going to a smaller vehicle for better mileage but in the long run I think I would be happier staying full sized. I would overload a smaller vehicle and maybe get 13-15 miles to the gallon if I was lucky and be less stable.