Had to chip in. We have a 2006 F350 CC DRW 6.0L Diesel, 5R100 Torque Shift Auto Trans, 4:30 LS Gears (GVW 13,000Lbs). We pull a 2006 Everest 364Q 5W that has a dry weight of 13,200Lbs. We just finished up our last trip from Memphis TN to Austin TX. Was a wonderful experience. Got 11.2 going, had a slight surging problem at 15 to 16Lbs boost. Took it to the dealer in Austin and they replaced the 'O' rings on 2 injectors. Got rid of the surging, and got just over 12 comming back. Not an oh-golly-gee-wiz milage, but considering what was being towe .... Without the trailer, we get just over 16 in city driving. The tranny is a 5 speed, and with the torque conver lock, it almost like a 6th gear. In tow/haul, we sill get all the gears, just the shift points are about 500 RPM higher and the shift is much more agressive. When letting off the accelerator and lightly stepping on the brake, the TC remains locked so you in effect have engine breaking, and it will down shift as needed to decrease your speed - especially nice in the stop and go traffic in city driving. First time it happened it really caught me off guard. we were going down a slight hill, and about the time I felt that I should start applying some brake to keep from gaining too much speed, the truck decided it was time down shifted before I even got my foot to the brake pedal ... almost caused me to lay a new set of rail-road tracks in my drawers.