I get 9-14 mpg empty 7-10 mpg loaded with my rig on the car trailer. I do live in the foothills tho so I have alot of hills. Its a 6.0l with the 4l80 and 4.10's on 285-75r16. The 6.0l never wants to shift in tow mode and it has all its torque at high rpm's. Sure my utility bed doesnt help.