My superduty was a 5.4 it averaged 8.5 mpg (3"lift and 35's on 20 " wheels) I have been impressed with the ecoboost since i brought it home.
picked up at dealer 6 miles
home 66 miles
towed my pathfinder approx. 5500-6500 pounds with car trailer. 166 miles
had to go get my bobcat on the equipment trailer approx 7500-8500 pounds. 250 mles
now I have about 400 miles and it pulled everything great. very happy so far.