 This 6.4L diesel F-250 is my fourth Ford deisel ( 2 - 7.3L's and one 6.0L ) and it seems to be the best engine design yet - had a slight fuel problem with the 6.0L.  The 6.4L has plenty of power and the truck rides extremely well. Mileage is lousy, only 13 - 14 mpg( 4WD hurts )but the trade off in power and safety and comfort are worth it. Especially like the navigation system, Sync, power folding mirrors, and interior roominess. Wife loves the heated leather seats. The tailgate step is great as are the 6" cab steps in the chrome pkge. I would HIGHLY recommend getting the electic auxillary cab heater ( one of the only options I passed up ), because of the increased cooling system capacity. HAPPY