8 would be great
7 might be obtainable
6 is realistic and probable
5 is the lower end
4 the lowest I experienced.
I'm anal about logging each and every gallon of gas - on all of the vehicles.
Anyone claiming 10 or 12 consistently on a 454 motor home either does not know how to fill the tank every time or doesn't know how to run a computer.
There have been reports here of 8.5 mpg's, but I'm pretty sure that was all at 50 to 55 miles per hour.
I get 6 to 7 (8 once or twice) at 55 to 60 mph.
Read this thread - http://www.airforums.com/forum...ad.php?t=14367
Do a search of related words including MPG and motorhome, you may discover a few more threads addressing this.