I had to make a run to the grocery store during lunch. So I did a little test, mpg as indicated on the EVIC. We know it's not perfect but mine has been very close so it gives you an idea of the fuel mileage.
I reset the EVIC and went to the grocery and back, 10 miles total. All back roads, 35 mph and one short stretch of 55 mph, hills the entire way. I ran the cruise at speed limit on every road. I accelerated slowly and stopped slowly. EVIC shows 14.9 mpg when I got home. So it's safe to assume actual mileage was between 14.4 and 15.4 as my EVIC has never been off by more than .5 in either direction.
Moral of the story, drive it easy and observe speed limits and you can get decent mileage out of this truck.