I would expect 6-7.5 mpg depending upon the chassis rating & gearing, whether your towing or not, lots of generator use or not, and level or hilly terrain. If you can get REAL 100% gasoline with no ethanol, bump that up to 6.5-8.5 mpg depending upon the above.
In any case, if you get more than the lower numbers of the estimates, you'll be pleasantly surprised. But don't expect it!
๐Oh, the generator pickup tube is usually set so that the generator cuts-off when the gas tank is down to about 25% full or 20 gallons left. If you're using the generator while travelling as is commonly done during the hot summer months, you'll want to make sure you refuel BEFORE you dip down to that level.
So, from a full 80 gallon tank, plan on refueling after about 50 gallons of driving, or 300-350 miles of driving. Usually, I start looking for gas stations when I pass the 300 mile point on a tankful.
~Rick
2005 Georgie Boy Cruise Master 3625 DS on a Workhorse W-22
Rick, Gail, 1 girl (27-Angel since 2008), 1 girl (22), 2 boys (23 & 20).
2001 Honda Odyssey, Demco Aluminator tow bar & tow plate, SMI Silent Partner brake controller.