How to Defrost Your Car Safely This Winter

Late for work again and your car windshield is frozen? Learn tricks for warming up and defrosting your car so you don't do any damage while trying to heat it up in the mornings.

Car needing to be defrosted

Photo by: Shutterstock

Winter can be hard on your vehicle. And not just because of sub-zero temperatures. Even if you routinely park in a covered area, snow and—worse—ice accumulations on your car can make your morning commute time-consuming and treacherous.

Why Defrosting the Car the Right Way is Important

On those really cold mornings, it can be tempting to step outside, start your vehicle, let it idle for a little bit and then hit the road only once the engine and the interior are fully warmed up. But does running your vehicle for extended periods of time under these conditions subject it to greater wear and tear? How much fuel does running your vehicle's heater and/or defroster consume, and how much more should you expect to spend on gasoline during the colder months? Overall, what's the best way to balance comfort, safety and economy when it comes to being a winter driver?

Defrosted Pipes of a car


To Warm, or Not to Warm Your Car

The Environmental Protection Agency (EPA) has studied fuel economy under winter conditions extensively. Its findings? Depending on the make, model and other technical specifications of your vehicle, you can expect your MPG to drop between 12 and 20 percent on days when the thermometer doesn't crack 20 degrees Fahrenheit. However, a variety of factors contribute to this lessening of fuel efficiency. Tire pressure, battery performance and oil viscosity are all affected by freezing temperatures, and all of these individual components can work together to transform even a hybrid vehicle into a gas guzzler.

Nevertheless, the EPA still recommends that drivers at least briefly warm up their cars on extremely cold days. As the Washington Post reports, however, sophisticated, computer-controlled fuel injection systems have replaced the traditional carburetor and its more finicky method of achieving the proper air to fuel mixture. Drivers of modern vehicles consequently no longer need to idle their cars for 15, 20 or even 30 minutes before running even a quick errand on a particularly frigid morning. As the EPA notes, in modern vehicles, "the engine will warm up faster being driven." And, if covered or enclosed parking isn't an option, you might also consider investing in a weather-proof or insulated cover to keep your vehicle from being completely exposed to the elements.

How Long Should You Warm Up Your Car in Winter?

The best source of information regarding whether or not, or how long, to let your vehicle warm up before driving remains your vehicle's manufacturer. Check the recommendations. And do remember that warming your car up for as little as 30 seconds to a couple of minutes, while it does burn fuel at 0 MPG and increases polluting emissions, isn't entirely wasteful. Brief idling does help to heat up and distribute motor oil that may have settled into a cold, hard lump overnight. Warming up your car thus helps protect your engine and extend the life of your vehicle. Again, check your manufacturer's recommendations, and, if you live in a region in which temperatures remain below freezing for extended periods, consult with your mechanic and make sure your vehicle is topped off with the correct motor oil—natural or synthetic—designed to perform at such temperatures.

Defrost Windshield of a car


Tips On How to Defrost Your Car Safely

Cold is one thing. But what about those mornings when you walk outside to piles of snow and ice on your windshield or even coating your vehicle from headlights to taillights? What's the safest way for defrosting your car and unsticking frozen doors, windows and locking mechanisms?
  1. Commercial deicing products. These products are abound and can be applied with a few quick sprays. Some deicers are even sold in a form that can be added to your vehicle's windshield wiper fluid reservoir.
  2. Scrapers. Scrapers come in a variety of shapes, sizes and materials. Some drivers swear by sturdy plastic scrapers, while others swear that nothing can ever replace a reliable brass scraper with a paper-thin blade—especially when it comes to that last bit of sheet ice that just won't budge.
  3. Water and alcohol mixtures. Water and isopropyl (or rubbing) alcohol mixtures (2 to 1) can also be employed as cheap deicing agents. Because alcohol freezes at a much lower temperature than water (-128 degrees Fahrenheit!), it is, even at what feels like room temperature, "hotter" than water at the chemical level. As the alcohol evaporates, it release energy, melting the ice.
  4. Dishwashing soap, water and alcohol mixtures. The addition of minute quantities of dishwashing liquid can further boost the effectiveness of this alcohol-water mixture. BONUS: These same alcohol-water recipes also work to unfreeze door locks. Coating your key in petroleum jelly before inserting it into the lock can help loosen it up, too.

Defrost doors of car


Prevent a Problem, but be Cautious

If you prefer to take preventative measures, you have many options here as well. Applying a quick coat of conventional cooking spray (which is simply aerosol oil, not unlike WD-40) to your door handles can prevent their freezing overnight. To prevent ice accumulations on your windows, some DIYers recommend spraying down your vehicle’s glass exteriors with a simple mixture (3 to 1) of vinegar and water. To protect against freezing locks, you can also create a moisture barrier by covering them with refrigerator magnets. (The old-fashioned, heavy-duty circular kind work best.)

Whatever method you choose, you should never try to force a frozen lock, door or window. Otherwise, you risk damaging gaskets, seals, motors and other complex mechanisms inside your vehicle. Be patient, and don’t expect to be able to get every last bit of winter precipitation off your vehicle in one pass. And be careful of creating slick spots on the road as you remove snow and ice from your vehicle. The larger the sheet of ice you sweep off your hood, the bigger the potential hazard you've created for other drivers. Most importantly, never pour hot water over a frozen window or door in the hopes of quickly melting the ice. You could ruin your vehicle’s paint finish, crack any safety glass that comes into contact with the hot water or even give yourself a steam burn.

Defrost Windshield Fog


What to Do After Defrosting Your Car?

So, you've finally gotten your car open, the engine humming and you’re ready to take the kids to school and head to work. But your windshield is so fogged up you can't see at all. What's the best way to defrost and keep your windshield fog-free? To defog your windows, you need to exchange the warmer, more humid hair—air you are making more warm and more humid with your body temperature and respiration—in your vehicle’s cabin for colder, drier air outside. Unfortunately, running your car’s heater actually contributes to this problem. The best and fastest way to remove fog from your interior windows is to change the balance of warm, humid to cool, dry air in your car. Turn off your heater, set your defroster’s temperature and fan or blower to high, fully open the defrost vent and make sure you aren’t simply recirculating air throughout the vehicle cabin. If your vehicle’s climate control system has a recirculation feature, switch it off and make sure air from inside the vehicle is being vented outside and that outside air is being pulled into the vehicle cabin—simply roll down your windows.

Once your windows are fog-free, you can roll up your windows, activate the heater and drop the defroster settings, but keep them at a lower setting to keep them clear. You don’t want to create a situation in which you are constantly taking your eyes off the road to adjust your defroster controls. The good news is that most newer vehicles come equipped with humidity sensors and will adjust automatically to keep condensation from forming on the inside of your windows once any initial condensation has been evaporated. You may need to activate these controls manually. Check your vehicle’s handbook or consult with your mechanic.

You can also apply commercial products that promise to block the formation of fog on interior glass. Look for products identified as anti-foggers or anti-fogging agents. Or, if you are feeling particularly adventurous, you can try an old scuba-diver’s trick and rub down the inside of your windows with the cut side of a halved potato. Finally, don’t mistake dirty windows for fogged-up ones. Regularly wipe down both the inside and outside of your windows and windshields with glass cleaner, and have your cabin air filter changed according to your vehicle manufacturer's specifications.

Although, a perfect excuse for staying inside to watch Netflix all day, a frozen car isn't an insurmountable challenge. Now that you know how to defrost the car safely, you don't have to be stuck inside all day. One last word of caution—practice extreme safety when driving in winter conditions. Just because you can, doesn't always mean you should.

Next > Enjoying A Snow Day


AHS assumes no responsibility, and specifically disclaims all liability, for your use of any and all information contained herein.

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