I got around 12.5mpg average coming from Eastern New Mexico to Northern California. Elevation did drop steadily the entire way, but i was very happy since i had an 18' open bed (around 2k by itself) with a 3000lb ford focus in tow.

We'll see what i get on the return trip.

 

I towed my trailer (27' TT / about 8,500 lbs) down to FL last week and got about 9 mpg round trip.

 

in my van[loaded weight~9 k lbs last week,400 mile trip-towing my 14x7 tall dual axle mx race trailer~6k lbs-12.5 mpg average with troyer's 93 octane tow tune

 

Just got a 32' Toy Hauler, and on the 400 mile trip home I got 9 mpg.