Both my 04 F-250 4x4 and my 06 F-350 SRW 4x4 with 3.73 gears and the 6L running Quadzilla chips at 120HP, 4" exhaust, and MAC intakes and filters get right at 16mpg average. My commute is 17 miles/25minutes and there is noting within 6 miles of my house so no short short hops. Best tank on the highway was 23.6 mpg.