So towing a small trailer with two bikes on it and a loaded bed I got 10.2L/100Km on the highway over 250Km. That is 23.6 MPG traveling for 156 Miles. I was doing 100 - 120 Km/h, 60 - 70 M/h
I will be doing a 1300Km trip in the first week of July hauling a 10 X 6 enclosed trailer with a weight of about 5000 lb over the Rocky Mountains so that will be a good test.