Just got the thing last Sat (5/8/04)... '04. 5 2500 4X4 QC LWB Cummins 600 48RE w/3. 73's. Mileage is just under 1K (had the oil changed for first time yesterday). Dealer delivered the thing with a full tank... overhead said around 15MPG. Topped it off last Sun with 21. 26 or so gals with around 350mi. on the clock ($34 @ $1. 59/gal)... overhead said around 15. 8MPG. Filled up for the first time (ran down until the fuel light came on) this Fri... . 30gal ($48 @ $1. 59/gal)... overhead said 16. 4MPG. The overhead reads low: Doing the hand compute that's around 16. 7MPG. It's combo miles, unloaded, and the thing isn't broken in yet. I drive like a maniac (75-85MPH on the highway), and already this thing beats the hell out of my 2nd gen Ram 1500 QC SWB 4X4 auto w/360CI gas job (when the overhead said 17MPG, it meant 15MPG) despite the huge weight advantage.