It's a shoebox shaped 28' RV. Does anyone see anything that can be done to help? They claim 15 mpg. I am going to run it on waste vegetable oil, my fuel will be free but it will be hard to fill-up for free on the road. That's why I want better MPG. I plan on putting in as big a tank as possible in it, maybe 200 gallons, which at 15 mpg will get me to Florida and back, but every little bit will help.
It might get crappy mpg as a car, but 15 mpg is FANTASTIC fuel economy for a house!
I'd say your only hope is Engine Off Coast whenever possible (although I hear that diesels use very little fuel at idle).
I think wheel skirts an a belly pan are some good ideas. It already is pretty low. I have to take a good look at it once I get it. I don't really want it to look too freaky, so no nose cone or giant wings! It only has 16" wheels so maybe I will get some racing hubcaps, if they will fit over the nuts.
I think also because it is so flat and square, I will have to cruise at only 55 mph.
Keep the ideas coming!
A roof faring, perhaps? Rear panels that can be opened up and extended out at highway speeds? If you want an idea of techniques to try, take a look at various concept aerodynamic big rigs and steamlined busses that have been built.
I remember reading in an SAE manual that a bus with a rounded rear end(bluff end I think it was called?) can achieve a .30 drag coefficient. If you can somehow get your camper into the low .4 range, you'd be in good shape.
Put a big old cone on the back and something on the front to soften the blow? Make it look more like a cross-section of an airplane wing, I guess, even if just a bit. It's not like RVs have to look pretty anyway,
A belly pan will do wonders under an RV. Those things have alot of things on the bottom that create alot of drag. Apart from that, ou need something on the back other than air tabs. You need something that doesn't cut off. A cone is a bit dangerous on something that size, but if you have a car in tow, it might be possible to do some sort of rear taper.