Starting up your car and allowing it to sit unattended to warm up is common practice, especially during cold weather waves like the one that Winter Storm Liam has recently brought to the Midwest of the United States. It is such a common practice that several states have implemented laws that make allowing a vehicle to sit idling on a cold winter morning illegal. These types of laws are generally implemented to deter thievery, but protection of the environment may be noted as a secondary motive.

In Ohio, where most of the FC&S editors hail from, the idling statute states that "No person driving or in charge of a motor vehicle shall permit it to stand unattended without first stopping the engine, locking the ignition, removing the key from the ignition, effectively setting the parking brake, and, when the motor vehicle is standing upon any grade, turning the front wheels to the curb or side of the highway." ORC 4511.661. This ordinance effectively makes even remote starter kits installed in cars, which thousands of Ohioans have installed in their cars, illegal. Many states offer exemptions to anti-idling laws during times of exceedingly low temperatures. Delaware is an example of a state with an exemption to the anti-idling law. In Delaware, a driver may idle his vehicle for fifteen or fewer minutes if the temperature is between -10 and 32 degrees, or for any amount of time if the temperature is below -10 degrees. Some of these laws are only enforceable on public streets; others are enforceable on personal real property, such as driveways.

Many people allow their cars to idle in order to allow the mechanics of the car to "warm up" so they run better when the car is driven in the cold. Contrary to this popular belief, from a mechanical standpoint modern cars are very different from vehicles of the past so idling could lead to mechanical problems to a newer vehicle. When a car is left to idle, the engine is not functioning at its full capacity, and engine cylinders and pistons might not have enough oil to make the car run smoothly, leading to mechanical issues over time. Additionally, car engines warm almost twice as quickly when being driven, then when left to idle.

For several years, Michigan law allowed police to issue a ticket for a parking violation warning on a car, if it was left unattended and idling in a private driveway. The law grabbed the attention of the public when a man received a ticket for a civil infraction, requiring the car owner to pay $128 for warming his car up in his driveway. Soon after, Michigan police announced that the department was going to be cracking down on unattended idling vehicles in order to combat car theft, as the law was initially enacted after a surge of car thefts resulting from vehicles left idling in their owners' driveways. Citizens of Michigan were outraged at the enforcement of this law, as warming up a vehicle is common practice, particularly during frigid Michigan winters. In March of 2017, a bill was passed that repealed the anti-idling rule in the Michigan Administrative Code. The bill ensured that the change would not modify the obligations of auto insurers that arose from the theft of an automobile. Drivers will continue to be encouraged to take measures to secure any idling vehicle, no matter where that vehicle is parked.

As for the environmental impact of idling, for every ten minutes a vehicle idles, one pound of carbon dioxide is released into the atmosphere. New York City generally has more idling than a typical city, but studies have shown that idling in NYC alone produces 130,000 tons of carbon dioxide each year. To offset that amount of pollution it would require 153 acres of forest functioning for a year. Also, the pollution that CO2 causes has been linked to asthma, heart disease, chronic bronchitis, and cancer.

The comprehensive portion of a standard Personal Auto insurance policy will cover the insured in cases of theft. Comprehensive coverage, however, is optional for consumers, and is an added expense that some drivers do not choose to pay for. Despite this apparent coverage, some insurers will deny a claim if the insured has displayed negligence in the course of the incident. Leaving a vehicle unattended with the keys in the ignition, and the door unlocked and the engine idling could definitely count as negligence in the viewpoint of the insurer. If an insured does have a ticket on their record for an idling vehicle, it would support an insurer's argument against the insured that the insured should not be compensated for the stolen car because they were not abiding by the law.