My newest one is averaging about 14 around town, about 19-20 on the open road as long as I stay around 70 mph tops. It's an Excursion that is chipped so a little to fun to putting a little extra foot into it when accellerating, kinda curbs the mpg's. The break in period is rather long. With my 350, I topped out at about 22 on the open road and 16 around town after about 25k miles. Towing my 19 1/2 predator, I don't see to much of a drop in the mileage, a couple miles per gallon probably.