I will give it this....if you keep your foot out of it, it really does give decent mileage. I do have a tow package, it is an fx4 with 3:73 gears... I just returned from towing a 6x12 loaded on the same trip i towed the car hauler on, and it did MUCH better....

 

"Fully loaded camper and truck 7/25/07 Roanoke Elevator
13,360#, full tank, 4 people, loaded camper w/water"

This is what I wrote in my maintenance log right before I left for vacation with my 28' travel trailer and '06 F-150 5.4L Screw, 4x2, 3.55, Edge #2 last summer. Took the whole rig over the local grain elevator scale.

Pulling it around IL and MO it has gotten between 8 and 10 MPG. It's no speed demon, but with the OD locked out it has plenty of power for the job at hand.

Biggest thing I see about the 150's and bigger trailer loads is stiffening up the rear suspension. Mine was all over the place wallowing until I added the Firestone Ride Rite air bags...35# in those and it's a different truck with the camper on!!!

I also run the Equal-I-Zer hitch and a Prodigy brake controller....I want as much control of the trailer built into the set-up as possible...the lighter F-150's are not nearly as forgiving as the heavier sprung 250/350 rigs.

FWIW, I find the 5.4L 3Valve to be a very nice towing motor, good low end torque for a gasser and plenty of power on the road, provided you accept the fact that you are towing a 7500# huge shoe box behind you and don't expect Mustang type performance.