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How Long Should You Warm Up Your Car in Cold Weather?

By Stephen Fogel, May 9, 2018

For drivers who live where the temperature drops below freezing, winter mornings aren’t much fun. Even worse, their vehicles have to deal with the cold, too. Drivers want their cars to warm up fast so that they’ll run properly — and so the heater will hurry up and work.

But what’s the best way to warm up your car when it’s cold? A lot of people believe you should let your vehicle idle until it reaches normal operating temperature. Others are convinced that you should let your car idle very briefly, then put it in gear and let it warm up as you drive. The truth is, just a quick warmup is best, in most cases.


There’s no need to wait long — usually

Most experts agree: With modern cars, you don’t need to idle for a long period before you drive off in the cold weather. Technological advances like fuel injection and better motor oil mean you can hit the road quickly if you’ve got a vehicle made in the last 30 years or so.

Most car manufacturers recommend taking off after the engine has been running for 30 seconds. Then you should drive gently until your vehicle is fully warm. This actually warms up your car much faster than if you were just idling it while parked.

It’s also better for your fuel economy. Think about it — when your vehicle is stationary and idling, you are getting zero miles per gallon. That’s as bad as it gets! Plus, there are reasons why extended idling can actually be bad for your car, which we’ll get into later.

So, why do people say to let it idle?

The idle-until-it’s-fully-warmed-up belief is based in fact. The problem is, those facts are more than 30 years out of date.
 
Up until the 1980s, automotive technology was more primitive. This made extended periods of idling a necessity, and over time this practice became conventional wisdom. There were a couple reasons why this used to be needed — and why it still is if you drive a car from that era.
 
Carburetors: Back in the days before emissions controls and computerized fuel-injection systems, most vehicles had carburetors. These devices sat on top of the engine, vaporized the gasoline and mixed it with air. The mixture was then sent into the engine for combustion.
 
Because carburetors, with their metal components, were exposed atop the engines, fuel would not vaporize well at low temperatures. This resulted in rough idling, sputtering and even stalling. Warming up the engine for a while warmed up the carburetor, letting it vaporize the fuel better. This was the only safe option in those days, so everyone did it.
 
Motor oil: The oil used in vehicle engines back then was much less sophisticated than what we use today. Low temperatures in those days would thicken engine oil to a molasses-like consistency. The oil needed to get warm so that it could circulate better through the engine and provide lubrication to all the moving parts. An extended period of idling let the oil heat up, flow better and help the engine run more smoothly.

»MORE: Find a certified mechanic near you

Cars have evolved

In the 1980s, increasingly strict emissions standards rendered carburetors obsolete. They were replaced by much more precise fuel-injection systems. This created a big change in the way engines operate — and how we get them started in cold weather.
 
Today’s fuel-injection systems are computer-controlled. They are able to recognize cold weather and compensate for it by providing a richer fuel mixture. The computer can also monitor the engine’s temperature as it warms up and adjust the mixture to suit. A high-pressure fuel pump guarantees the proper vaporization of the fuel. The cold-weather starting process is now much more reliable, with minimal time needed for engine components to warm up before being driven.
 
The quality of the motor oil in your engine has improved since the ’80s, too. The demands of increased fuel economy have resulted in thinner grades of oil. These not only reduce friction for better mileage, but also flow much better at low temperatures. In fact, the latest fully synthetic oils are able to flow easily at temperatures as low as minus-40 degrees Fahrenheit.

Why idling can be a bad thing

Despite these advances, the notion of idling to warm up your car has stuck around. The truth is, it’s almost never necessary these days. In fact, there are several downsides to prolonged periods of idling:

  • It lets the richer gasoline mixture strip the oil from the engine’s cylinder walls, increasing engine wear
  • A rich mixture from a cold engine can damage your catalytic converter
  • Your vehicle pollutes a lot more when idling in cold weather
  • Long periods of idling are illegal in most places and could get you fined
  • Fuel consumption increases, so you’re wasting gas
  • Idling is the slowest way to warm up your engine and your oil

But notice that we said “almost never.” We admit there are a couple situations where it’s a good idea.

When idling may be necessary

It’s a big country, and winter means different things in different places. Many of you may experience mild winters, where the temperatures don’t get too far below freezing and there isn’t a lot of snow or ice. But for folks living in the northernmost latitudes, winter means long stretches of subzero temperatures and major snowfalls.
 
If you deal with very extreme weather, you may need to idle for longer periods of time, especially if your car is covered with snow or ice in the morning. Issues of safety and comfort come into play here. You’ll need to remove the ice and snow from your vehicle before you drive away. You’ll also want to be sure that your windows will stay clear once you’re driving. And you want to get your heater is cranking.
 
For these reasons, a longer period of idling will provide you with safer driving conditions. Simply start your car and take a few minutes to clean it off, if necessary.

Use common sense and stay safe

For most of us, most of the time, there’s no need to let the car idle for long in order to warm up. Whatever type of winter weather you have, use the appropriate technique for your conditions, and put safety first.

7 User Comments

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By , January 15, 2011
I don't entirely agree with your comment. Exhaust gases coming out of the engine are corrosive. If the exhaust system is cold and doesn't get time to heat up the moisture that comes from combustion (your exhaust pipe ever drip water ? Hmm-m) becomes corosive and will quickley rot the pipes out. Given enough time to heat the exhaust system up, the moisture stops dripping out as the gases can stay in a gaseos state and muffler lives for another day. Short hops are the worst thing for a car. Some of what you say I agree with but what little gas you're saving might be negated by the increased costs of buying and installing exhaust system replacements plus the costs of building the system plus the cost of disposal. Kinda knocks the snot out of that "livin green thing".
By , April 14, 2011
Cpete, When idling or driving a vehicle when cold, condensation will form in the exhaust system. More exhaust flow through the exhaust system while driving a cold vehicle will actually warm the exhaust system faster that if you were to let the engine idle until the exhaust system warmed up.
By , December 13, 2013
Jim is right. Whether you idle till warm or drive out straight away condensation will still build up. The quicker the engine warms the sooner the condensation is reduced. Increased exhaust gas flow will clear the condensation faster. Yes short hops are the worse thing but a slow warm up doesn't help.
By , December 10, 2014
Thanks for the info,like a lot of people I worry about just about everything.I was always told to let my car warm up I live in the south so we don't get the sever cold like other places.I have been letting my care warm up for about 5 minuets before driving and I only work 3 miles from home warm up time as long as drive to work!!!!!!!!
By , January 08, 2015
Yeah, I've never heard what you just said.... I've asked experts this and they say, let it sit there, and not to force it to run right away... its like human before a workout; warmup the muscles
By , November 30, 2015
My problem is condensation from my Ford PU in cold weather. The only condensation that I have ever seen on other vehicles is from the AC in summer. But water just runs out of the splash plate during warm-up. Then, nothing. ???
By , March 23, 2017
This advice here works for a car's engine, but not for the transmission. Specifically, an automatic transmission. Not sure about a manual trans, but you can actually damage an automatic transmission if you drive off all the time without warming your car up. In winter, the 30 second rule does not apply to the transmission. To operate at optimum level, a transmission needs about 4-6 minutes for it's fluid to warm up in winter. In summer, depending on how hot the outside temp is, you can use the 30 second rule.

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If you let the car sit and warm up idling for about 2 - 5 minutes, then it will drive. will not drive before that. ...