Usually running 75-80 mph with 38's and 4.56's nets me about 8.8-9 mpg on the highway.
On the way down from NC to Florida, I purposely kept the instantaneous mileage showing so I was constantly aware of how hard I was pushing the pedal.
Even while running almost 80 for 90% of the trip, I averaged almost 11 mpg.
I was thrilled to death. I was driving 68-72 for the first tankful and averaged almost 12 mpg. WOW.
I can't wait to put the supercharger on. I won't have to have the truck go into overdrive on the hills... should use even less gas.
Mark