Every moment you spend idling your car's engine means time spent needlessly wasting gas, as well as rougher wear on your vehicle. So give it a rest, and avoid idling through your days.

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. (Even though Environmental Defense found that idling for more than 10 seconds wastes more gas than is required for startup.) But, 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. That doesn't count the damage done to idling engines by incompletely burned fuel.

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.

the daily green: the consumer's guide to the green revolution; friday, january 23