Just got back from a 600 mile road trip. With 22" I got 14 MPG. All highway mileage. I was monitering the average GPM. It was dropping lower and lower when going across Aligator Alley when I was doing 95mph.:shhh:
I've got 20" rims and no engine mods of any kind and I get 15.3 - 15.5 mixing highway and city. I haven't taken a road trip yet as I just got the truck a month ago. Road trip is scheduled for Thanksgiving.