Tuesday, July 7, 2015
Physics that affects mileage
Vapor pressure. In summer, gas companies produce a blend with lower vapor pressure--less likely to evaporate in the heat. This reformulated gas (fewer short chain molecules) gets you slightly better mileage. But costs a little more.
Friction. The faster you go, the more gas you'll need to move the same distance. Steady at 80 uses eight times the power of steady at 40.
Drag coefficient. Basically this means ho easily air flows around the car. You want as little frontal surface as possible. So an aerodynamic front--as opposed to a boxier make--means less gas.
Momentum. Cars. Whether an 1,800 pound Smart Car or a 5,000 lb SUV, cars have a huge amount of mass. Once a car gets going, you can use momentum to cut gas usage. Savvy drivers don't jam on the gas when a light is changing--they let momentum carry them to a stop.
Rolling resistance. Most of your speed is to counteract friction. The tires are where that happens. Hard tires would be less friction, but would also have less braking force. You have some power over resistance by inflating or deflating your tires. Themanufacturer has balanced performance, efficiency and ride handling--so follow the tire instructions.
Temperature. A/C is a power guzzler. Some people turn the air off a minute when making an acceleration turn.
So...Jackrabbit starts and stops and enormous speeds on the highway--good way to burn a lot of gas.