Every moment you spend idling your car's engine means time spent needlessly wasting gas--for every two minutes a car is idling, it uses about the same amount of fuel it takes to go about one mile. It also means creating emissions, as well as rougher wear on your engine by incompletely burned fuel.
One of the ways the much-praised Toyota Prius is able to achieve such impressive fuel economy is by having a computer cut out idling automatically: when you aren’t making headway, the gas engine shuts off. For regular cars, it doesn’t make sense to shut off the engine at every stop sign. Environmental Defense found that idling for more than 10 seconds wastes more gas than is required for startup. You should certainly kill it when you are waiting for your date to finish getting ready. Or when your honey has to run into the bank to cash a check.
Overall, idling Americans burn 2.9 billion gallons of gas a year, worth around $78.2 billion, according to a recent report from Texas A&M.
Many communities have organized "no idling zones" around schools, churches and other locations. At least 15 states, and many counties, have laws that restrict idling for large diesel engines. New York City and New Jersey have laws limiting idle times of passenger vehicles, but enforcement is lax.