I just got a 08 f-550 and it runs around at 16500 lbs all the time, I don't have any complaints about power, although the milage is bad, but I can't really expect good milage travelling at that weight. My buddy just bought a brand new Dodge 3500 with the 6.7 Cummins, and guess what, he is getting around 9 mpg as well, so it isn't just Powerstrokes that use fuel!