Should I Let My Car Warm Up Each Morning?

| 10/1/2008 12:00:00 AM

Tags: cold start, gas mileage, engine warm up,

Snow CarIs it best to let my car warm up in the morning when it’s really cold? Or does that just waste gas?

Logan Widmore
Pocatello, Idaho

Although you might think it’s easier on your car to let it sit and gently warm up, doing so is a bad idea for a number of reasons. Most importantly, it does indeed waste gas.

The vast majority of cars on the road today use electronic fuel injection. When your car’s engine is cold, the computer tells the fuel injectors to stay open longer, allowing more fuel into the engine to help it run cold. As the engine warms up, the injectors let in less fuel and everything returns to normal, so to speak. 

The problem is, letting your car sit and idle is the slowest way to bring it up to operating temperature because it’s generally sitting in your drive at just above idle speed. And this method to warm up also invites other problems. Remember that modern cars are equipped with a multitude of devices to help them run clean, including a catalytic converter (sometimes three of them), a device in the exhaust system that works to burn off unburned hydrocarbons in the exhaust stream. A cold engine emits a far higher percentage of unburned hydrocarbons than a warm engine. Unfortunately, the average catalytic converter can’t process 100 percent of unburned hydrocarbons even in the best of times. Importantly, the catalytic converter needs high exhaust temperatures to work properly. Throw in a cold engine emitting a high percentage of unburned hydrocarbons, repeat several hundred times, and you can end up with what’s called a “plugged” converter. In a nutshell, the converter becomes overwhelmed and literally ceases to function. This won’t happen all at once but over time, the end effect is the same: poor mileage and significantly dirtier exhaust.

The best bet? Even when it’s 10 degrees F outside, start your car, let it run for 30 to 60 seconds to get all the fluids moving, then drive off gently. Your engine will warm up faster, your exhaust system will get up to temperature faster so the catalytic converter can do its thing, and you’ll use less fuel. Which is what you wanted all along anyhow, right?

8/30/2014 8:27:49 AM

Car engine warm up needed for car starting and generally we are focused for the best cars and the servicing point to be for that. So just for better service select the best alternative car station and the mechanics.

5/22/2013 11:09:37 AM

I agree with this article - idle running is a waste of fuel and harms the environment and eventually us who inhale all these dangerous fumes. I live in Sweden and winter is quite cold.  We could have -4 to -13 degrees fahrenheit or even colder and Idle running is only allowed for 1 minute here in order to minimize air pollution. The best and most effective way to warm up a car on a cold winter morning is to install an electric engine heater together with an interior heater.  I have this installed in my car and it's really a blessing to hop in a pre-heated car not having to scrape the frost and snow on the windshield, windows and rear window every morning.  All I need to do is plug in the heater in a wall contact with a timer (30 minutes to 1 hour will do)  and voila -the car is ready for use!  I'm attaching the link of the 2 leading companies who manufacture and sell this equipment.  I highly reccomend these products.  It will not only give you warm comfort, but it also makes the engine happy by minimising engine wear due to numerous cold starts, as well as saving the environment.


5/12/2013 12:29:38 PM

accually! i just boughht a used (modern car) and it makes a weird ticking sound when its running, well it turns out the reason it does this is because the previous owner would basically turn the car on and drive away without letting it warm up for a few minutes. modern cars have aloty shorter pistons then older cars, older cars have long pistons so there stable going up and down the cylenders, modern cars have shorter pistons so when you drive off when its cold the pistons arent going up and down properly in the cylender there wiggleing from side to side causing this to wear your pistons! you definitly need to warm up your car befort you drive it!! if you dont your pistons eventually will sound like mine! its nothing huge, i was told to use thicker oil and use a lucas oil stabilizer to protect the pistons from more wear. carefull what you read and hear look into every aspect of it.

robert demaio
3/26/2013 3:42:20 AM

my honda odyssey has 355500 miles on it and i just started and drive off even at 10 below. has the original converter and passes inspection each time

michael mckelvey
1/24/2013 5:47:57 PM

If you can safely start your engine and drive after a minute (while you check your car for any issues, flat tires, fluids, warning lights, mirrors, etc.) and clearly see out each window and mirror, then that's great.If temperatures reach the likes of -40, then idling is necessary. You need the heat from the engine to drive and keep the windshield from freezing up. If you need to use your wipers, you better be sure you have heat. Also, while the engine bay is warming up, the power steering fluid will warm and allow you to steer. Tires will be out-of-round until they soften, and shocks will be very stiff since the fluid in them are nearly frozen. Hydraulic fluid in your braking system needs the heat from the engine bay. So both arguments are correct depending on the temperature you are dealing with. Plugging in a block heater and battery blanket only help the coolant and battery, but there are fluids required for safety that are commonly overlooked. I doubt you'll ever see a Prius in the arctic, it won't last a day...

jp mc
1/24/2013 6:54:42 AM

from what iv read ,i think a few minutes in below freezing temp is a good rule of thumb, and is what everyone probably ends up doing anyway. just enough to start the warming in the engine and get everything off RIGHT away and your cold inside anyways. wait 10-15-20 mins and your wasting gas and time. it does make sense that driving it slowly and gently will warm it up faster than idling it, then you get momentum also to help. as for the pistons and cylinders shrinking in cold weather im not too sure, i guess its just a question of how cold it has to get to change the size where it makes a difference if it even does.also time do you want the pistons pumping for 15 mins before they warm up, or speeding up the process after 5 mins or so?

stephanie dickson
1/20/2013 4:42:16 PM

Hmmm... I wonder if my car friends agree...

peter kiryluk
1/9/2013 1:27:01 PM

Its not a good IDEA to drive your car when its cold at all, metal is brittle when cold and acts differently, driving your car will make things act differently, oil, trans fluid, pumps. When things work they get warm and work better. You invite a world of hurt and you will kill your car at 150,000 following the advice above. You really need to warm it up. Construction equipment runs 2 times its life if you just let it warm up before you go. Its a matter of what happens to things when they get cold. It may be a waste of fuel, but you can spend 15 cents or, you can spend 200 on a part or more.

mohamed foda
12/27/2012 8:59:55 PM

I have jetta and it's written in the manual to switch on and drive.

john & virginia ledoux
11/24/2012 11:13:23 PM

They're idiots.

barrie templeton
11/24/2012 5:01:55 AM

Right, and then extra load of the easy motion of the car will help it warm up faster - and get you going toward your destination. I also believe that idling, whether the engine is warm or not , whether in cold or hot weather, causes wear t the engine, especially to the top end, where thvalve train is. This is because the oil pump, at idle, does not provide as much pressure as it does at normal engine speeds, and the valve train, with its many bushing and bearing surfaces, may not get enough oil. The result is premature wear to those surfaces, which makes noisy engines and increases oil consumption.

alaskan attic
11/23/2012 7:25:17 PM

Up here in Alaska, we have block heater and some also have battery warmer. We just plug in our cars when it is cold for a warm start in the morning. Works great if you have it all on a timer. Keeps the wear and tear out of your engine.

robb phillips
11/23/2012 4:45:54 PM

best reason I have found for letting my car warm up a little before starting out on a cold winters day is saftey On a cold winters day if the engine is not up to proper running temps and if for any reason you should have to increase/ decrease speed in a hurry your chance of stalling in cold weather by moving with a cold engine increase,this in turn ,may cause an accident in heavy or lite traffic or even cause you to lose control of veihcle control

marcus robinson
2/17/2012 7:50:09 PM

Despite what Experts and Mechanics say, I have heard that it is not good to let your car warm up before you drive it. i actually just heard it online for a New York State Defensive driiving course. Believe it or not!

james peter
1/24/2012 12:04:51 PM

Do you have any sources for this? I'd love to save the time and money by not waiting for my car to warm up, but I've always heard information similar to the comments above. I'd rather wait a few minutes before driving off if that's what is better for my car in the long run.

chris spory
1/23/2012 8:53:17 AM

Seriously dumb!

chris spory
1/23/2012 8:50:50 AM

Wasting gas? Warming an engine will increase the engine life by 30%. I've been doing the research for the last 25 years.

jake jordan abongan
1/21/2012 1:19:40 PM

how would you know if it's time to take off? what is the ideal time frame of idling a vehicle sitting for 12hrs in a weather of -30celcius and above?

patrick poe
1/19/2012 1:54:52 PM

If I can clear out my one car garage/storage unit, then I could park my van inside, which would help significantly. Ain't realistically happenin' though.

patrick poe
1/19/2012 1:53:03 PM

Where I live, we have to scrape, and sometimes shovel off our windows. That alone isn't enough. My breath will freeze to frost on the inside of the windshield. I live close to work, and my truck won't get warm enough to clear it off. Prolonged idling is the only workable solution, until I can get electric heat installed. The "wasted gas" is just a part of the cost of living here.

john & virginia ledoux
12/20/2011 3:20:21 PM

Your are just plain dumb.

john & virginia ledoux
12/20/2011 3:16:43 PM

Warm your engine for 3 minutes when the temps are 20 and below. Drive away after 30 seconds, 20 and above. When it's - 30 warm the engine for 10 minutes and if you can leave your transmission in neutral, so the fluids have a chance to warm up. Use synthetic oil year round!

whitney rearick
12/19/2011 9:22:38 PM

No, don't wait for the defroster, you're just putting more hydrocarbons into the air and getting 0 MPG. SCRAPE your windows. Many of us live in areas with crappy air quality, and idling cars contributes significantly to the problem.

jim ward
11/27/2011 4:34:45 PM

Oval-shaped pistons? Very funny. Not. This certified mechanic says that's hogwash. The best reason for warming up your car on a winter morning is SAFETY! Defrost your windows so you can see out each one of them before you drive anywhere. DOH!

t brandt
11/27/2011 3:09:15 PM

I'm getting a kick out of observing how resistant we can be to the debunking of long-believed myths. The whole concept of "warming up an engine" goes back to the days of points&plugs when a cold ignition simply would miss too often to allow us to drive away quickly after start up. Those of us who ever took a course in calculus know why the concept of "letting the parts expand as they warm up" is simply wrong. Most engine wear occurs on that first cold crank before oil pressure comes up. By the time the engine ignites, there's plenty of pressure. One shouldn't just fire it up and drag race, but allowing it to idle for more than a minute or so is just wasting fuel. Drive away easy; the engine doesn't know if it's standing still or not and the thermostat won't open until it hits the right temp anyways, regardless of the car's motion.

john galt
11/27/2011 2:19:35 AM

another overlooked item is ALWAYS warm your car up with the windshield defroster on. Todays economical thin glass windshields will crack or shatter if the car is warmed up with the heater on then switched to defrost when needed. AND as previously mentioned the transmission, transfer case, power steering and engine oil all need to get up to temperature before putting them under load. Also it is always a good idea to park where you do not NEED your parking brake as ice and snow can build in the wheels causing your brakes to freeze in the on position which is very dangerous on icy roads

michael heward
11/26/2011 4:29:23 AM

Yes, you should allow your vehicle to warm up before driving off cold. All of the engine componets need to expand slightly to prevent premature wear. The cylinder walls and pistons change diameter as they warm up. A cold piston is smaller in diameter than a hot piston. Even with modern CNC equipment, you have to undersize the metal componets to allow for expansion once everything warms up. In other words, your engine is slightly loose when cold. As it warms up, the metal componets expand. Another big ticket item to not overlook is the tranny. If you have an automatic, not only does the fluid need to move, it needs to function in a hydraulic sense. Want to kill your tranny before its time, just keep starting up cold and driving off. I have always allowed my vehicles to warm up for 15 to 20 minutes and have never suffered a blown converter because of it. Even so, I would rather waste a little extra fuel and I will take my chances with the converter rather than the many thousands of dollars for a new engine or tranny!!! Cedar Mill Bumper and Hitch

barry brown
11/25/2011 6:25:31 PM

During cold weather, you should allow time for the power steering, transmission & engine oil to warm enough to flow easily. Most vehicles will startup with a fast idle and once it returns to a normal idle (~ 700 RPM) it should be warm enough to gently take off and drive away slowly. We you see your temperature gage start to move or after approximately five minutes, everything should be warm enough to drive as normal. That's my 30 years of automotive experience.

glen graham
11/14/2011 9:41:17 PM

My Land Rover is fitted with an electric heater & pump - it is fitted into the coolant line and runs off mains power. I've got it plugged into a timer socket which sets it off about 10 minutes before I come out on the coldest winter mornings. It heats the coolant up and circulates it, so the engine is nicely warmed before I even first turn the key to start it, the engine oil is already warming up etc (though not the grea oil of course, so I still take a steady drive away). It also means that I get warm air out of the the heater straight away - something which old Land Rovers are not exactly known for! They may last well (mine is 26 years old, works in the forest off-road and is in every day use and has outlived many much newer steel bodied 4x4's by many years and shows every sign of lasting another 10 or so) .........but the cabin heaters are junk! :-)

tyler olsen
10/22/2011 1:43:36 AM

Here we run into a problem, cost vs. cost. As the article says it does use a little more fuel, and over a long period of time it can cause the catalytic converter to fail, however, the reason for allowing your vehicle to warm up for a few minutes is not to heat the car, its not to defrost the windows, and its not to allow the fluid to flow. Even though these are all good reasons, the biggest is this: When your car is cold, the cylinders of your engine are NOT perfectly round, they are oblong or oval shaped. This is bad because what happens is that as the piston (which is PERFECTLY round) moves up and down, it rubs or wears on the cylinder walls more in certain areas. This causes 2 problems: first is that it wears your piston rings unevenly, and second, it wears your cylinder walls unevenly, causing a loss of compression, reducing fuel economy, oil consumption, and smoke from the tail pipe. The time frame for this is about the same for the damage to the converter, but the cost of a new engine compared to the cost of a new cat is HUGE! $7000 opposed to $800. Oh, and one more thing about this article, a bad catalytic converter will not always cause bad fuel economy, unless it is plugged, but they can just burn out.

roland green
1/25/2011 2:35:44 AM

It's been pretty cold here in Ireland - more frost and snow than we've seen in a 100 years. The reason we warm up our vehicles is to defrost them and clear the ice off windscreen and side windows so one can see to drive. Scraping often doesn't work as moisture in the air immediately freezes on the cold screen and you have to scrape again after travelling a couple of hundred yards. Getting the cabin nice and toasty is a benefit.

lee r
1/23/2011 11:10:00 PM

I think most people warm up their cars so they will be warm when they get in! I have wondered about this for a long time. I never warm up my car and now I don't feel so bad about hurting it. What really bothers me is seeing people in summer sitting in their cars eating lunch or reading with the car running and the air conditioning on! I hate that!

out in the sticks
1/22/2011 8:32:52 PM

I understand some of the issues of living in a cold climate, having lived in Alaska and other colder climate areas and I bet Logan in Pocatello, Idaho has some pretty frosty mornings to contend with. I won't go into the things we did when it got really cold, but single digit temperatures above 0 F didn't need extraordinary measures. Maybe magnetic block heaters or something similar to keep the oil liquid. All are things that will help protect your gas or diesel engines happy as far as having frosty windows go we used something called an ice scrapper to remove ice from the windows and mirrors, or you can put something on your windshield, blanket or something to keep the frost off. Another thing that was handy was a small squeegee or towel to remove fog on the inside of the windows and there is a product that kept fog from forming on the inside of windows. That all being said, i bet i could still come up with some sort of excuse to idle my vehicle for extended periods of time

1/21/2011 6:54:58 PM

Here's what I do... I place a small ceramic heater on the armrest facing forward to the window. I plug it in to an extension cord (through a slightly open window, I have weather guards so no snow comes in)the cord goes to a power strip in the back porch. 30 minutes before I go to work in the morning (4:30 am!) I turn the power strip on. My car doesn't get very "warm", but I haven't scraped a window all season :D

tim nelin
1/21/2011 1:12:40 PM

The other problem is, what do you do if you have a diesel that should be warmed to near operating temperature before using? If you don't properly warm a diesel engine before using it, you risk all sorts of potential harm to it's internal components. Cold oil and internal components that expand with heat are issues that Diesel engines require we consider. The reasons for using the diesel engine are things such as efficiency, power, longevity, and generally, a more environmentally friendly power source. Hmmm.

cathy koos breazeal
1/21/2011 12:42:09 PM

A minute or less is insufficient time in snow country. We usually upright our windshield wipers, so they thaw more quickly. Even with a light skim of ice and 15-20 degrees, it takes a good 10 minutes to defrost the windshield sufficiently for safe driving. Cathy Sierra Nevada Mountains of central California

dan bokenko
1/21/2011 11:42:50 AM

Are the people that tell you not to warm up your cars from Pheonix or Miami? Just breathing in a car on a cold morning is enough to fog your windshield making it unsafe to drive. Even just a little fog refracts street and head lights reducing visibility. I have tried to not warm up my car, but the savings don't justify the risks. A couple drops of gas is nothing compared to two cars smashing into each other. Often on snowy mornings, just getting out of the driveway is enough to warm up a car, but most days I give it 5 minutes while I scrape frost from my windows and headlights.

1/21/2011 10:18:10 AM

I've often wondered the damage I was doing in warming up my vehicle....not so much of what I was doing to the vehicle, but to the environment. Warming it up was for the point of thawing it out - get the encased ice/frost off, but then only driving the kids a short distance to school. Seemed silly. My eldest child told me that it was pointless to warm it up for the oil pressure etc. etc., but not being into mechanics, I didn't understand all of that. This winter, thus far, I've only let her sit and warm up on the days we have a 'go, go, go' schedule in the morning and I just leave her sitting, thawing out, for 10 minutes before we go. Doing too much damage I think, to continue this practice. Thanks.

bill goodrich
1/21/2011 8:55:38 AM

Drive off gently is the key phrase. Until the transmission is warmed up good you are wreaking havoc on the internals. Changing the fluid(still important)does not protect the trans near as much as gentle acceleration on cold mechanical parts. Because if that I would say 2 minutes warm up in the winter.

yasel perez
12/27/2010 6:49:53 AM

thats all fine and dandy, but want to know something else? The real reason why we warm cars up is to buil oil pressure. think about it. ever wonder why most cars fail befor 200K? oil. or oil related. i hope my comment had a usefulness to your understanding. thank you.

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