Idling your car to warm up the engine is unnecessary.
Research from the Environmental Defense Fund shows that today's electronic engines do not need idling to warm up before being operated, and in fact, idling creates both unnecessary waste and harmful pollution. With today's modern engines, idling for more than 10 seconds wastes more fuel than stopping and restarting the engine.
Rob Maier, who runs Maier's Garage in Bridgeport, Connecticut, says, "You don't really need to idle your car, because of the efficiency of modern fuel injection, which eliminated carburetors and chokes. The only reason to let the car idle at all is to get the oil circulating, but after 30 seconds that's a done deal. My truck has 150,000 miles on it, and I just throw it into gear and go."
Never warm up a vehicle in an enclosed area, such as a garage. According to Esquire.com, "Idling a car in a garage, even with the door open, is dangerous and exposes the driver to carbon monoxide and other noxious gases. If the garage is attached, those fumes can also enter the house."
Temperature is rarely a reason to idle these days. If you're like us and just don't like driving in a cold car, Bob Aldrich of the California Energy Commission points out that "idling is not actually an effective way to warm up a car — it warms up faster if you just drive it." Turn on your heated seats instead!