Me and the finance company have a 2001 Dodge 2500 4x4with the 5. 9 comapart eng 3. 54 gears. Pulling a 97 Jeep on a 16 ft car trailer Max speed is 75 t0 80 mph at 2200 rpm at 9 to 10 mpg. This is on South Fl. flat land. Had it checked at local Cummins dealer His computer read out stated average...