I know this really doesn't help much for the OP problem, but just throwing out my theory here. I've seen problem after problem with RV's through the years about paint, leaks, fading, dry rot (paint/tires) etc. I really think the best investment one could make before buying an RV would be a FULL COVERED metal storage building to house it in. Your paint will stay new. Your tires will last longer. Your tire cover etc., will always look great. You won't get bird doo, debris, or sun damage on the roof & A/C unit. Also it won't form leaks. I really believe a coach like this could last many decades if not a lifetime.
4 whopping cylinders on Toyota RV's. Talk about great getting good MPG. Also I have a very light foot on the pedal. I followed some MPG advice on
Livingpress.com and I now get 22 MPG! Not bad for a home on wheels.