Take the 2-minute tour ×
Skeptics Stack Exchange is a question and answer site for scientific skepticism. It's 100% free, no registration required.

There is a belief among a lot of people that you should start your car and leave it on for 5 minutes before moving it in the morning. Is this practice good for the car in any significant way, or it is just a myth?

share|improve this question
4  
    
I noticed with one of my previous vehicles that if I didn't warm it up in the morning, it would sometimes stall or the engine would make funny noises. It was an older vehicle, and my mechanic explained that it needs a longer warm-up because of the high mileage. –  Randolf Richardson Nov 25 '11 at 8:06
2  
@RandolfRichardson, just a note. I am really talking about new cars (1-3 years old) and effects on it if I dont warm it up for 5 min. I understand if a car has malfunction, it may need proper warming. –  client9 Nov 25 '11 at 15:09
add comment

1 Answer

up vote 22 down vote accepted

No

Once upon a time on old car engines this was required, and piston engined aircraft warm up because they stress their engines to the maximum as the first thing they do. But this is no longer necessary for modern cars. The recommended warmup time vary between 15 seconds and three minutes.

Canadian Department of Natural Resources:

Contrary to popular belief, excessive idling is not an effective way to warm up your vehicle, even in cold weather. The best way to warm it up is to drive it. In fact, with today's computer-controlled engines, even on cold winter days, usually no more than two to three minutes of idling is enough warm-up time needed for the average vehicle before starting to drive

The Globe and Mail:

"get into your car, start the engine, and while putting on your seat belt, getting comfortable, checking your mirrors and turning on your radio, 30-45 seconds have passed, so put it in gear and off you go"

Toyota Canada, [...] representative said it’s not necessary to warm your vehicle, nor will doing so cause any harm. The rep adds that there are pros and cons: the motor and oil will warm, and the coolant will flow – but idling for long is harder on the environment.

Australian Broadcasting Corp:

The Canadian Office of Energy Efficiency agrees that the best way to warm up your engine is to drive it. Even if the outside temperature is -20°C, they recommend that you idle the engine for only 15-30 seconds before you pull out onto the road.

share|improve this answer
1  
This was going to be my answer, actually. You'd have to have a car older than 20 years old for this to make sense. It used to be the case that there was a very high likelihood of making the engine stall if you didn't let it warm up first (even with Automatic transmissions), but now engines refuse to allow coolant to circulate until they've reached a certain temperature. –  Ernie Nov 25 '11 at 16:48
2  
My understanding is that it's about curburetters v fuel injection. Curburetters get the fuel/air mix wrong when its cold: fuel injection doesn't. –  DJClayworth Nov 25 '11 at 20:46
1  
Must mention the link by @MetaEd, here it is again cartalk.com/content/do-cars-need-warm-cold-winter-mornings was helpful in choosing this answer. –  client9 Nov 27 '11 at 19:33
1  
This does not address the viscosity differences in oil at low temps. If the oil is too thick due to cold there is still a risk of engine damage when the engine is stressed. Which I believe is why there is still the recommendation of allowing the car to idle for a minute or so. –  Chad Nov 28 '11 at 20:21
2  
Which I believe is why there is still the recommendation of allowing the car to idle for a minute or so - But it is not mentioned explicitly as to how much time is required. In my observations until you get to 0F/-15C there is not much of a change and some of the lighter weight oils probably have less congealing though that is all conjecture and I would love to see some real results. Which was why I commented. Your answer was good and addressed the warming of the coolant but did not address the oil substantially. –  Chad Nov 28 '11 at 21:57
show 6 more comments

protected by Community Mar 25 '13 at 7:11

Thank you for your interest in this question. Because it has attracted low-quality answers, posting an answer now requires 10 reputation on this site.

Would you like to answer one of these unanswered questions instead?

Not the answer you're looking for? Browse other questions tagged or ask your own question.