Just returned from a 455-mile trip across north Florida. Flat from Jacksonville to Lake City then hilly (definitely NOT mountainous even like the Blue Ridge) from there on toward the Apalachicola River where we stayed. The first 266 miles took 30 gallons to get the tank as full as I could. That would be 8.7 MPG to which I say No Way. I budget stops using 7 MPG, but have seen 7.5 - 8.? on some trips. This is a 31-ft scaling at 14000 towing about 3000.
I used to set Cruise at 62. Now I find that if I don't use cruise I can keep it between 55 and 65 pretty easily and it looks like I do at least 1.0 MPG BETTER than cruise. My target speed is 60-65.