Keep the engine running.

A cardinal rule for getaway drivers; bad advice for the rest of us.

Law enforcement agencies around the U.S. have been gearing up for the seasonal uptick of “puffer” thefts, where thieves steal a running vehicle after its driver leaves it unattended to warm up. (They’re called puffer thefts because of the puffs of exhaust vapor that come our of a car sitting in the driveway in cold weather.)

It could be because you want to de-ice the engine for a long trip, let the heater work for a warmer drive, or finish an errand that you know will only take a few minutes.

But whatever the reason may be, leaving your car idle isn’t worth having it stolen.

It Could Happen to You

It may seem like a red-flag mistake, but drivers leave their cars vulnerable to theft more often than you’d think.

The National Insurance Crime Bureau (NICB) says that 1 out of every 5 stolen vehicles had keys in them, while nearly half of vehicles were unlocked when stolen.

And another NICB survey says that 1 out of every 3 drivers have left their cars while their engines were running.

“People are basically handing over the keys to their car as a gift to auto thieves to steal,” said Lt. Colonel Scott Hernandez of the Colorado State Police, which is part of a task force combating puffer thefts.

Pennsylvania authorities reported that about 20 cars in several townships were recently stolen when left idling, some at convenience stores and others in residential driveways. Only four of the stolen vehicles were recovered.

In a separate incident with more favorable ending, Ross Township Police, also in Pennsylvania, recovered a stolen Lexus that went missing after the car’s owner left his unlocked vehicle running in his own driveway. Police reported finding the car at a mall less than a mile from where it was stolen.

But it’s not just typical motorists who can be caught unawares.

Last summer, a Los Angeles Police Department cruiser was stolen while it was running before the thief crashed it into a Starbucks and totaled it.

This type of car theft even hits motorists in the U.K., where thieves behind the crimes are dubbed “ice bandits.”

Am I Covered?

The comprehensive portion of your insurance policy will cover you in cases of theft, but is an optional purchase for consumers. The Insurance Information Institute says that 3 out of every 4 drivers in the U.S. decide to buy that additional portion of their car policy.

For those with comprehensive coverage, studying your policy’s wording will be crucial in puffer incidents.

Some insurers will deny a claim if you have displayed negligence in the course of the incident, and leaving your keys in your car could count as negligence.

An insurer trying to prove negligence can turn to local laws and/or ordinances. In some towns across the U.S., it is a ticket-worthy offense to leave your car unoccupied with keys in the ignition or a running engine.

Doing so in Seattle is illegal. Eau Claire, Wis., has a similar law, but it is only enforced on public streets.

In Lynn, Mass., first-time offenders can be fined$35. In Northglenn, Colo., that fine can be as high as $499.

So read up on your local laws, since they vary widely and may be important in the claims process. If an insurer is trying to prove that you didn’t take reasonable care in preventing the car theft, having such a violation/ticket on your record could help your carrier’s case that the stolen car doesn’t warrant compensation because you weren’t heeding the law.

Tips for Prevention

Those wanting to avoid that hellish experience of opening your front door to an unexpectedly empty driveway should consider the following prevention tips:

  • If you want to be covered for most instances of vehicle theft, get quotes for comprehensive coverage.
  • Don’t leave your keys in your car, leave spare keys/valuables in plain sight, or leave your vehicle unattended.
  • Consider purchasing a remote starter or similar device that allows a car to run without the use of a key.
  • Be extra wary before your morning commute. In Arvada, Colo., officials reported that most of their puffer thefts were around 7 a.m., when frosty mornings make it easier for thieves to spot the exhaust from the tailpipe of an unattended car.