I have surrendered. I found a Unimog L5000 in the Netherlands, that at half the weight of my Pete, will pull the same weight with less hp. It's a crew cab with a 220hp with 650lbs torque, 8fwd/6rev manual (yea) fitted with Michelin 445/70 R24 tires.
I fully expect this new BluTec diesel will be a more satisfactory 15-18mpg.
Years ago I had a smaller Unimog that I used on the farm for plowing and general use. At that time, when diesel was $0.99/gal I was getting 28mpg - b/c the highest speed I could attain was 50mph.
Pete 378 - 43 Jamco LQ horse hauler
Unimog L5000, 220kw MB, 16 sp