I crunched some mpg numbers for the trip. Keep in mind, most of the weight was in the bed of the truck rather than in the trailer. So, while these numbers will reflect hauling a brick shaped thing behind me, the numbers are more for hauling than towing. With the trailer, it weights 1,200#, with a 80# manual log splitter, 72# Badlands Off Road Jack, 40# 48" Farm Jack, an electric chain saw, and a plastic tub with recovery gear in it. So, not much weight, just drag.
To Land Between the Lakes, I averaged 14.9 mpg and from LBL, 14.7 mpg.
For the off road portion, I got about 12.9 mpg.
If you are hauling a trailer bigger than a 4'X8'X2' box, your mpg will likely be worse. The trailer also had a vinyl tarp of the top with bows to support the tarp. Fuel usage would have been higher if the box had been uncovered.
With these ecoboost engines, you are either in eco and getting the roughly 24 mpg or you are in boost and fuel mileage drops like a rock.
Compared to my 2011 that I drove to Truck Nationals with the empty trailer in tow, I got about 16. Normal highway mpg is somewhere around 19.