18 mpg Dodge while towing?

i have tried for 20 years to get someone to prove their fantastic mileage. No one has ever done it. All I tell them is to come hook on my 31W Arctic Fox which weighs around 10K loaded and we'll go to Ohio via I 68 and back to VA. If he can get the bragged about 19 MPG I will pay the fuel bill. It is scientifically proven because there is a formula for BHP and fuel burn and you cannot get more than 115,000 BTU/gallon of #2 diesel. I get 10.9 Westbound from VA to CO on I 81-I 40-I 25-NM 550. That's with a Chevy Duramax turned up to 440 HP and driving 67 mph.
We also have AIRLIIFT air bags and love them.