My time to brag -- I had a 1989 Chevy 3500 CC dually 4x4 454 FI with 4.56 diffs that got 15 mpg (8 on hiway and 7 in city = 15 right) and no real change towing 5 k horse trailer. My 1990 Champion class A w/454 carb got 8.5 mpg. We would take MH with amenities over p/u. We now have 2010 Ram 3500 CTD 4x4 SRW megacab pulling 14k 5ver getting about 11.5 mpg towing at 55 mph in 5th at 2k rpms. Headwinds and hills drops to 9.5 mpg. I agree about the speed. The faster we go the worse the mpg. When we drive 62 non towing its about 20 mpg and at 75-80 mph it drops to 17 mpg. You can't have speed an economy at the same time. The long right pedal is the deciding factor!!