The bottom line is.....diesels are made to tow. A V-10 is a fart in the wind compared to a diesel. I make just under 24 MPG w/ no load, w/boat 18, w/ boat and camper 15.5 (all highway). Difference in fuel every 10K about $500 in favor of the diesel. Considering a V-10 acutally makes 11 mpg, I'm guessing about 8-9 mph under load.

When towing, a properly maintained diesel may out last a gas vehicle by tow fold. Now do the math.