Anyone have any idea why I would get 3MPG better on the front tanks over the rear ones in my 97 f250? 460 motor, 197K miles. Truck runs great but consistently shows this difference no matter how I test it. It's even worse when towing or running the AC in town.

 

heres what you do. rig up a fuel transfer system from the rear tank to the front tank, place an actuator switch in the cab. then you can transfer fuel to the front and always run off the front which gives you 3mpg better milage.
Or you can recalculate your milage as this doesnt seem likely.

 

Is the rear tank empty when you use the front tank?.just the weight difference with the empty tank may help, but i doubt it helps that much.