Update: I replaced my wide 17" mud terrain tires with a set of 18" take-off wheels and tires (Goodyear Wrangler) from a 2017 f250 and on my July trip through Idaho and Wyoming I averaged almost 15mpg. In addition to noticeably better mpg, I have a smoother and quieter ride and the truck still did great off-road.dharte said:2005 F250 Power Stroke-On my first big trip in March, (2,000 miles through Death Valley, Nevada and Utah) I averaged about 13.5mpg. On some of the 70-80MPH highways I had really strong headwinds and mileage went as low as 11mpg on some tanks . Before I got my Hawk, I had a regular camper shell and I would average about 15mpg. I wish there was a way to reduce air drag....