Perhaps the biggest reasons are convenience and that our rules of thumb for driving cars derive mostly from a time before electronic ignition became universal. If you recall when you learned to drive, you were probably told by your parents or your instructor that turning off and on the car repeatedly would (1) wear out the battery, (2) wear out the starter, and (3) waste gas. Today, nearly every car uses electronic ignition and none of these three concerns exists any longer.

Save Money

Frequently restarting your engine does negligible damage to the engine and does not drain modern batteries excessively. In fact, the opposite is true; idling an engine forces it to operate in a very inefficient and gasoline-rich mode that, over time, can degrade the engine's performance and reduce mileage.

Direct Reductions from Eliminating 5 Minutes of Idling

Estimates of the amount of time we voluntarily idle each day we drive range from 5 to 10 minutes per car. In just 5 minutes of idling we can burn between a half and a whole cup of gasoline, depending on engine size. Over the course of a year this adds up on average to as much as 10 to 20 gallons of gas. By not voluntarily idling 5 minutes per day, we can save between about $60 and over $120 per year per vehicle, assuming a price of $7 per gallon of gas.

In addition to these direct savings, to estimate the total financial impact of reducing voluntary idling, two additional factors must be added in. First, as noted above, wear and tear costs from the increase in engine restarts need to be considered.

Second, there is also the reduced fuel efficiency and possibly shorter engine life that result from voluntary idling. For the average car for the average mileage driven for each vehicle type, the estimated reduced efficiency results in an additional $80 to $160 per year in fuel costs.

Improve our Health

Emissions from idle cars can cause health problems. A link has been found between contaminants in vehicle emissions and significant respiratory health effects. Poor air quality and smog, caused in part by vehicle exhaust are resulting in increased hospital admissions, respiratory illnesses, and premature deaths. Children are more vulnerable to air pollution, because they breathe faster than adults, and inhale more air per pound of their body weight. The poor air quality also causes problems for the elderly, and those with respiratory illnesses such as asthma, emphysema, and chronic bronchitis. If unnecessary idling stopped, then the air would be cleaner, and respiratory health would improve.

Save the Environment

Not only is an idle engine costly, it has significant environmental impacts. Idle cars emit exhaust gases such as carbon dioxide. A car's engine idling for 10 minutes produces about 90 grams of carbon dioxide and consumes 0.14 liters of fuel. If all cars left their engines running for a minute less each day--or 365 minutes less a year--approximately 225,200 fewer tons of carbon dioxide would be emitted, and 350 million liters of energy would be saved among those vehicles.

Voluntary idling is one of the many daily actions that seem negligible but that, when taken cumulatively, can have a large impact on total emissions of carbon dioxide and on the environment more generally. As mentioned above, the waste that results from needless voluntary idling is most easily seen on a cumulative basis.