I have a 2000 f250 4x4 atuo super cab long box 3.73 gears on vacation this Aug. running empty on a 231 mile run I got 21 mpg. The return trip I got 20 mpg this was on mix of speeds from 75mph to Yellow stone pk.45mph in Yellow stone park back to 60mph in Wy. on our way to Cody,WY. We left from McAlester,Mt.