This was on the interstate running a true average of 60 mph. A stretch with a lot of hills. About a thousand lbs in the bed. 210 cu in cummins 6 cyl turbo diesel putting out 120 hp with gm 4 spd manual SM 465 trans and a sterling/ford 10 1/4 rear axle from a '92 F350 with 4:11 ratio. First road trip with my creation. Of course I'd be out rollin' in this rig even if it got 10 mpg. Just sayin.........