Drive like you have no brakes. And steady on the loud pedal. This works with an OTR tractor trailer as well as a Prius. I work with a guy that's on and off the throttle in step with his never ending conversation. He gets lousy mileage and his gimmick air filter and programmer do nothing to help it.
Assuming proper maintenance and tire pressure...
I've seen as high as 14.5mpg with my F250 city, 17 interstate and 9.7 towing. Unfortunately for me, I don't have the patience to tow 58~mph so towing mileage is usually 8-8.5 at 65mph.
I average 53mpg with my Pruis at 50-100 miles a day so I'm not too concerned about the F250's mileage towing. Wife drives the F250 16 miles a day. That's my solution to the mileage conundrum.
We got 7.9mpg on the way down to Fort Desoto Park campground this week with a moderate headwind. Worth every penny! :B