Towing my 34' Avion triple axle trailer, loaded, with a quad in the back of the F-350, 7.3 liter powerstroke truck I get about 11-12 mpg. The same setup with my 1994 Dodge one ton dually with a Cummins engine would get 14 mpg pulling that trailer. I miss the Cummins engine but I don't miss the truck.