My first rig was a 2000 Tiffin with the older V10. My constant mileage average was right about 9 mpg. Even towing my wife's car on a dolly to Bar Harbor and Moose Head Lake in northern Maine I got just over 8 mpg. My best reading coming home in no hurry after a Memorial Day weekend was 11.9 mpg averaging about 40-45 mph, 225 mile r/t. My present rig with the newer V10 (362 hp etc) I just peg my average at 7 mpg, no matter if I'm towing the toad or free wheeling, 7 mpg is what I base all my travels on. I don't bother with even keeping my mpg anymore after each outing, only gallons used and $$$ spent on fuel per trip.