I've got a 2000 CC 4X4, 3.73, auto, heavy duty everything. On the last trip to Dallas, with a 20 mph headwind, 75mph, 13.5 mpg. Trips to New Orleans, 80 mph, cruise on, 4 full size adults, with a weeks worth of luggage and junk, average 15.5 mpg. I've got no complaints, other than minor items for the dealer to fix under warranty. I switched to 5W30 Mobil 1 at 10k, this engine performs way better than I expected. I will say the gas mileage was not an issue when the 6500# truck was purchased, although every little bit helps. I think it was a better truck for me than the diesel next to it would have been.