I'm pulling a new Flagstaff 26FKWS with a 2012 F-150 Ecoboost. Most recent trip was 2800 miles.....9.1 mpg for the trip.
Like walking uphill both ways to school (in the snow) as a kid, I seemed to be bucking headwinds everywhere.....spending four days on an island in NW Houston TX (17.1 inches in 10 hours....heh,heh....checking for leaks).
So....to the question:
My sweet spot seems to be about 62 mph -- kinda where air resistance, shift points, mileage, and power seem to cross.
In defiance of conventional wisdom, I am running a 3.31 rear end. Sounds horrid for towing, but ..... that's why god made transmissions: to choose your gears.
We are blue highway types and hit interstates for no more than a couple hundred miles on the trip. Owned big clunky motorhomes and tight little TT's for 40+ years. We think (hope) we have finally found the ideal combo, though may update TV from time to time.
For us, RV'ing is not a destination, but the travel....lots of roses to smell out there (even played music at Luchenback last week).
2012 Ecoboost Screw, 3.31 (yes....really) rear end.
2016 Flagstaff 26FKWS, about 7500 loaded
Retired AF Mustang.....Picker always looking to jam.