If your car is parked and idling for more than 10 seconds, turn it off. Even though you're not driving at fast highway speeds, a car that's "on" but not moving is still using a quarter- to a half-gallon of gasoline per hour. It also releases emissions that can be harmful if you're parked where people are gathered. Every little thing you can do to save gas adds up, so turn off the car if you're not immediately going anywhere.
ANDREWS MCMEEL SYNDICATION