On August 16, 1998 a stock Chinook motor-home, with only slight modifications, set a new recorded land speed record (sanctioned by the Southern California Racing Association) of 99.776 mph. This record was set at a density altitude of 5,384 feet. Adjusting to sea level the speed would have been 108 mph.
Most motorhomes regardless of year and size get 5-10 mpg. The class A motorhome are the lowest while the class C motorhomes are a little higher smaller motorhomes also get the best mileage. There are two exceptions to this. One is Diesel Motorhome often get 10-12 mpg. The other exception is class C motorhomes on Toyota Chassis they can be a little hard to find but deliver 14-16 mpg the trade off is the Toyota chassis uses much, much smaller engines than other makes sacrificing power to deliver better fuel economy. Some Toyota based motorhome owners complain of going very slowly up mountain passes. Remember that motorhomes may get very poor gas mileage but they are not daily drivers so unless you plan on using your motorhome on long trips the gas is not that big of a problem overall.
One for Mr Sooz a motorhome towing a small car with this sign on its back window: "I'm a good car. I go where I'm towed to go.