My in-laws have a 2007 34-foot Holiday Rambler diesel pusher, and they average 12 mpg (and that's towing a vehicle behind them). From what I've read, a comparable front-mounted gas engine would average around 6 mpg. On top of that, the diesel engine will probably just be getting broken in when the gas engine hits the end of its useful life. If I were in the market for a Class A, I would have to be able to test drive a gas engine before I even considered one. I imagine that a 34 foot bus towing a small car with even a V10 gas engine (much less the GM 8.1) would struggle in the terrain around here. I've never driven my father-in-law's "A" (nor do I want to), but I've been behind him, and he could easily maintain 75 mph on the interstate if he wanted to (he doesn't, FWIW). I guess my point is that there is a reason why gas-engine-powered Class A's are less expensive than their diesel counterparts.