Speeding is a major factor in fuel economy. You might get to your destination more quickly if you're going 65 versus 55 miles per hour (104.6 versus 88.5 kilometers per hour), but you're decreasing your car's fuel efficiency by around 15 percent while you're at it.
For every 5 miles (8 kilometers) per hour you're driving over 55 (88.5), you're essentially raising your gas prices by 21 cents per gallon, and that's assuming the price at the pump is only $3 per gallon. Of course, 55 miles (88.5 kilometers) per hour is just an average. Calculating your car's ideal speed for fuel economy is much more complicated. The ideal speed tends to be between 40 and 60 miles per hour (64.4 and 96.6 kilometers per hour), with sportier cars topping out at the higher speeds and larger vehicles at the lower end of that spectrum.
Speeding is just one way that your driving style can guzzle gas, but how else can your driving habits impact your car's gas mileage?