I've owned a '95 3.9, A-500, 3.23 reg cab and a '01 3.9, 5 speed, 3.55 ext cab and they were both consistent 20 mpg trucks (50/50 city/hwy driving), as opposed to my '97 5.2, A-500, 3.92 reg cab at 14-15 mpg. I towed my Spirit on an open trailer the 80+ miles to Norwalk several times with the '01 with no problems - it wasn't a Cummins, but it had decent power. Odd thing about the '01 - it got poor mileage and had no power till it hit 500 miles, then it was like you flipped a switch; I got noticeably better mileage and power, as if it had a "valet mode" in the computer so you couldn't abuse it until it hit a certain mileage and was broken in.