Thor Forums

[Beau388]

I traveled for 16 years in one of the most aerodynamic class A coaches ever produced a UltraVan; eight feet wide, eight feet high and twenty two feet long. All aluminum semi-monocoque construction, it weighed 3,500 lbs empty. It had a 164 cuin (86 hp) air-cooled engine in the rear. Fuel mileage averaged 16 mph on 91 octane gas for the 188,000 miles my wife and I put on it.



If you don't travel above 60 mph, aerodynamics does little to help fuel mileage. The cd for a flat plate is 1.0, the cd for a Class A is in the range of 0.85 and for a car it is about 0.40, so it sounds like aerodynamics matter, but frontal area a much bigger item in total drag than the cd coefficient. At 60 mph under standard conditions aero drag contributes about 8% to the total fuel consumption. Tire flex is the biggest contribute to rolling resistance. Putting 15 more pounds of air pressure into your tires will increase you mileage more than any aerodynamic shape at 60 mph.