I had a Super Duty V10 4x4 that I loved, raced and beat rice grinders over the pass from Vegas and got in the low teens for gas mileage. I bought a 26' toyhauler with a 2 seat sandrail in it in Grand Junction Colorado so I went up to tow it home. Coming home on the I-70 I was pedal thru the floor board, going down hill, rpm's screaming, and doing 45 mph! Plus I stopped at every gas station between Co and Pahrump. I stopped 4 or 5 times to check brakes and bearings on the trailer thinking something was locked up, even thought the tranny went out on the truck. The closer to Vegas I got the faster I could go, doing 60 mph or so down into Vegas but stopped on the way out of town to gas before I could get home to Pahrump.
Problem was no turbo at the high altitude and I didn't check but I am guessing I was getting about 4-5 mpg. Towing around Pahrump, Vegas, Dumont was better for power and gas mileage was still under 10 mpg. Tranny was always shifting up and down and rpm's were maxed to get the power to tow, even that light hauler.
Traded the Super Duty in on a Dodge cummings and what a difference! I get low to mid teens mpg towing my 32' toyhauler 5th wheel full of toys, water, grub, etc and I have all the power I need. No red line rpm, no shifting up and down as there is enough power/torque to just go down the road and no problems at high altitude with the turbo.
I will never own another gas truck but I had no idea about the difference in power until I owned one, a friend tried to tell me but I said yea whatever. Does it pencil with the cost of a new truck, high diesel prices, and $52 oil changes at the dealer? No but to me it is worth it. If I hadn't towed the hauler from Co I would probably still have the V10.
I have 30,000 miles on the Dodge and the only time I go to the dealer is to get the oil changed.