We get about the same on our E 450 V10 when I am towing our Jeep Unlimited. But on flat roads without the Jeep in tow, we get 7-7.5. thrown in a mountain or a head wind and all bets are off. not sure there is anything I can do. I usually drive 60-65 MPH using TowHaul most of the time when pulling the Jeep.
__________________
|