Thor Forums

[Beau388]

Rolling resistance, aerodynamic friction and drive-line efficiency all work together to determine fuel mileage.
Rolling resistance can be separated into tire pressure, tire design and vehicle weight. The higher the tire pressure, the less the tire flexes and the less energy is lost as heat, but the ride will be sacrificed. For class A tires there is little difference in tire design. Wide singles instead of duals give better mileage but not much, so the less tires touching the road the better. About 70% of the tires rolling resistance is determined by weight, so lighter is better. Rolling resistance does increase with speed but it is linear. That is why the tires get hotter the fasted you drive.
Aerodynamic friction can be divided into bow wave and surface friction. The smoother the surface the better. Wax does help. Any protuberance on a flat service causes increase in resistance (drag). Rooftop A/C, vents, antennas all contribute to resistance. The greatest drag per square foot in the front is a flat plate and the best is a cone and the same for the rear. Although Aerodynamic drag is very small below 45 mph, but increases as the square of the speed above that. As for making an aerodynamic tail on an RV, see the Kammback aerodynamic effect.

Gasoline engines are most efficient at WOT, as the act of reducing the airflow into the engine causes a decrease in engine efficiency. That means you want the smallest displacement engine that will do the work required. The more gears in the transmission the better as they are able to keep the engine in the best operating range for the power required. All torque converters generate heat when not locked up. Generating heat means using fuel. The looser the torque converter (loose torque converter generate more torque multiplication than do tight torque converters), the more fuel is used.
Anytime you use the brakes. you are turning energy into heat. The less you use the brakes the better the fuel mileage.
Just some tips for better fuel mileage. Some of these things are easily done, others require modification and some are never practical.