Bad thing is, a gas engine is a gas engine. I bought a new Tundra 5.7 V8 in 2010 and it's got LOTS of horsepower, gets 20 MPG highway driving but when I hook up my MIL's light weight aluminum 2 horse bumper pull with my 700lb. Polaris ATV in the trailer, fuel mileage drops to 9-10 MPG. But I can put 3 horses in my slant load 3 horse gooseneck heavier steel trailer and still get 13 MPG using my '91 F250 diesel. And my diesel has always got 18 MPG highway driving empty. Guess if it's mainly used for towing a diesel still makes more sense.
Heavy truck and diesel mechanic (thankfully retired after 30+ yrs)
'91 F-250 SC 4X4, 5spd. ATS Turbo, 3:55 diff.