You have to look at MPG over the long haul. I’ve driven my 98 Itasca over a 99 Ford F53 just over 48,000 miles in 8 years and have kept a meticulous mileage log. It shows single fill ups of 12.11 to 6.03 MPG with the first year average going from 8.45 to the current year’s about 8.00.
Here are just a few factors that will affect MPG, terrain (flat or hilly land), speed (the faster you go the lower the MPG), starting (jackrabbit to gradual), how level the MH is when filling fuel (leaning toward the pump or away) and the sensitive & volume of the gas pump nozzle (ease of kick off).
I’m hoping that my MPG goes up a little as the MH just hit 100,000 miles and I’ve had the plugs replaced.
Dave