My average with the F150 Ecoboost and Elkmont (with 2 kayaks on top) over 6565 mi is 12.2 mpgUS. Our previous Tacoma's mpgUS was about the same (over maybe 12,000 mi). I rarely exceed 60-65mph when towing.
Our absolute worst mileage was two consecutive fill-ups one day when fighting headwinds in Manitoba. We averaged 9.25 mpgUS on that day, and the poor Tacoma just struggled, even though I dropped our speed down to ~50-55mph.
The Rockies were nothing compared to the Prairie headwinds. Unfortunately on our way back east through the US prairies, there was little prairie tailwind.
