I had a 99 F250 2WD 4.10 rear, during the years (99 to 2011) I owned it I towed a 10,000 lb 5er over many passes. Running empty, on the highway I got about 14 mpg Running loaded, with passes and headwinds it would drop as low a 8 I consistently kept the speed down, seldom over 65. The 99 (and 98 in fleet vehicles) has a different crank then the 2000 and produced the lower HP