Tips for Starting Your Car in Subzero Weather


If your car wouldn't start this week because of the subzero temperatures that gripped much of the country, now would be a good time to get ready for the next bout of frigid weather.

NHTSA Bids You Safe Travels With Winter Driving Tips

Among the best moves you can make to improve your car's chances of starting the next time the temperature plunges below zero are to make sure your battery and charging system are in good shape and that your engine is using the grade of oil recommended by the vehicle manufacturer.

That advice is from Mike Calkins, manager of technical services for the AAA travel group's national office, who suggests your odds will improve even more if you add an electric battery blanket and/or an engine block heater to your anti-winter arsenal. "In winter temperatures, your battery is far less effective, and the load your engine needs to crank over is much higher because the oil is real thick. If your engine is cranking slowly, you should take it in and have the battery checked, especially if it's more than 3 years old," Calkins said in a telephone interview.

"After three years, your battery has lost some of its original reserve capacity, so it's a good idea to have it tested," he said, adding that extreme cold weather can reduce a battery's remaining capacity by more than one-third. "Basically, electrons, just like people, slow down when it gets really cold outside. The chemical reaction inside the battery that creates electricity just doesn't happen as fast when it's cold."

At the same time you have the battery checked, Calkins said it's a good idea to have the alternator and charging system looked at and make sure the battery terminals are clean and the cables are in good shape.

"This time of year you're driving in the dark more hours of the day, and there are more loads on your electrical system. The battery doesn't recharge as quickly because there are other things taking up the power," he said. "You need to make sure the battery and charging system are in top-notch condition."

Using the right oil is important because most modern engines call for high-viscosity oils such as 5W-20 that flow easier in cold temperatures. Some vehicle owners prefer heavier oils, such as 10W-30, but Calkins said thicker oil puts more strain on the starter motor and battery. Heavier oil can also increase engine wear because it takes longer to reach its normal flow rate than lighter-weight oil.

For those who have access to an electric outlet where they park overnight, Calkins said electric battery blankets can prevent or reduce the loss of reserve cranking power caused by frigid temperatures. Prices vary from about $25 to well more than $100.

An electric engine block heater also can be effective, making the engine easier to start and delivering warm air to the heater and defroster outlets sooner. Calkins said engine block heaters are almost universal in northern locations such as Anchorage, Alaska, where motorists can plug their engine heaters into outlets at parking spaces. He estimated that engine block heaters run from $150 to $200, including installation One traditional recommendation for dealing with arctic conditions has been to use alcohol-based gas-line antifreeze that absorbs moisture in the fuel system. Calkins said that they work, "but today they're unnecessary.

"Over 95 percent of the gasoline today contains up to 10 percent ethanol, a form of alcohol. That alcohol is already in the fuel and absorbs any moisture. So essentially, today's gasoline has gas-line driers, as they used to call it, built in. There's no reason to buy something and add it to what's already there," he said.

Calkins also downplayed other conventional advice, such as covering a car's hood with a tarp or blanket to keep the wind out and parking the car in a sheltered area, out of the wind.

"When a car sits for 10 hours or 12 hours overnight, it's going to be the same temperature [as the ambient air], and the wind chill doesn't really affect the car. People feel wind chill, but ultimately a car is only going to reach the same temperature as the air around it and not get any colder," he said.

The real trick to starting an engine when the thermometer is below zero is to have a well-maintained car.

"Today, any modern car, even when it's zero degrees outside, will start within one or two engine revolutions, provided everything's in good condition," he said.

Among other recommendations that AAA lists for winter driving are:

  • The cooling system should be filled with the proper mix of antifreeze and water (usually 50/50) and capable of providing freeze protection well below zero.
  • The heater and defroster should be in good working order not only for your comfort but because in frigid weather the windshield and other windows can frost up - and you won't be able to see where you're going.
  • Likewise, a working windshield washer system filled with fluid that doesn't freeze and good wiper blades are necessities to combat the snow, slush and salt that accompanies nasty winter weather.
  • Even if you're confident your vehicle meets all those requirements, AAA suggests carrying emergency gear just in case. Among the items the organization says you should have with you when you travel by car are gloves, boots, blankets, flares, a small shovel, a flashlight and high-energy snacks.
By Rick Popely | January 8, 2014 | Comments (8)



What happened to dedicated North/South batteries?
It saves corporations money by having to develop only one for the entire 48 contiguous states, but everyone ends up with a compromise.


Which cars in the last 20 years have a 50/50 mix of antifreeze and water? Some vehicles use transmission fluid for the cooling system. I would follow the owner's manual not AAA.


The article was about starting in extreme cold weather and not a mention of turning off all other electrical draws during starting like the heater fan, lights, radio, etc.



Please enlighten me which vehicle uses the transmission fluid for the cooling system. Very interested to learn how did they do it.

On the other hand, it is common for hydraulic power steering to use transmission fluid...

Rick Popely,

Battery blanket and engine block heater don't work very well for those who do not have a garage.


I was going to ask Jay the same thing. I have never once seen a passenger car or truck come through my shop that uses ATF to replace antifreeze. The lines you find running from transmission to the radiator are cooler lines, to help with ATF temps in the transmission.

It is still the industry standard to use 50/50 mixed antifreeze in the radiator, whether it be OEM fluid or multi-vehicle compatible aftermarket brands.


I'm assuming hes referring to The Red coolant that some fords have been using or the Orange Dex cool found in some Chevy. Its not Transmission fluid. Its specially formulated Antifreeze and will not mix with the "Green" stuff.

Car man

@Lance when you turn the key to start the car it disconnects the power to the accessories and has done that for years

Car man

Watch your headlights and your heat or air everything turns off so when you crank the engine the starter has full power

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