Remembered why I got a F450 with 4.30 gears ... observation.

My F450 unloaded barely made 10 mpg, F250 was making 14 easy, reaching 16 and i did not drive F450 faster than 65 mph as above the mpg was taking nose-dive.
450 was DRW, 250 was 4WD
Measuring mpg while hauling 18k in my case was not reliable, as most of the trips were in 100 miles range, so not full tank.
Still F250 had gearing to pull 18k trailer at freeway speeds on overdrive.
I used to own small pickups that require downshifting with head wind, so I know what over or undergearing is.