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Exactly Why You Need To Warm Up Your Car When It's Cold

Jalopnik logo Jalopnik 1/3/2018 Jason Torchinsky

© Getty Cold winter is something nearly everyone seems to have an opinion about. We’ve tackled the issue before, and I’m still on Team Warm, but there’s still a lot of controversy around this important question. Let’s take another look.

The big argument against warming up your car before driving off on a cold morning is that, essentially, modern cars can handle it. And that’s not wrong—a modern, fuel-injected car with today’s sophisticated engine management systems can accomodate startup in very cold weather quite quickly.

Oh, and if you don’t have a modern, fuel-injected car, and drive old carbureted relics like myself, then there is no question: warm that thing up. Let it idle for a minimum of five minutes before you take off. Get that oil splashing around in there. Give that carb a bit to wake up and stop freaking out. Don’t rush it.

There’s a few reasons why a carbureted car wants to take more time to warm up in very cold weather: first, it’s likely older, and that means getting less-viscous oil to as much of the engine as possible is even more important; same goes for getting some heat into all the cold, brittle rubber hoses and connectors and so on.

The big reason is that in the cold, gasoline doesn’t evaporate as well, so the gasoline is harder to vaporize when cold, and can go into the cylinders in liquid, droplet form, where it will cling to the walls and do nobody any good.

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When the engine is cold, the combustion is uneven and poor; the carb chokes off some of the air to compensate and runs richer, but less efficiently. As things heat up, everything starts to improve, and once the car is warm enough, the fuel can properly vaporize, and the car starts to idle and run smoothly. This just takes some time.

Even on a brand new car, you’d still likely want to wait 30 seconds or so for that cold, molasses-thick oil to work itself up from the oil pan, but, generally, it’s true you can start up and drive off, and that the car will warm up quicker when driving.

I agree that this is accurate, and I also think it’s still a bad idea, and you should let the car idle for at least a couple of minutes, maybe five or so.

Why do this, when the car can technically handle a near-immediate takeoff? Because being able to do something and that something actually being good are two very different things.

The same goes for not letting your car warm up a bit. Even if the car can start and drive nearly immediately, every rubber thing in that engine is still hard and cold and brittle, those fluids are still highly viscous, and while driving is possible, putting any load on that engine isn’t doing it any favors.

It’s not just me saying this—actual intelligent, non-morons agree, like the folks at Team O’Neil Rally School, who drive cars in sub-zero weather all the time:

Look, if you know you can drive it gently while the engine gets up to temperature, fine, have at it: but for most people, we don’t really know.

Will you need to accelerate suddenly to avoid danger? Who knows? It could happen. Will you have to detour and end up going up a steeper hill that requires more power? It can happen. And, remember, any hill will put your engine under load.

Ultimately, what’s the point of risking it? Why put yourself in a position where you could be needlessly causing engine damage?

Even well-written, well-researched articles that are against warming up, like this one from PopSci, admits that taking it easy for the first five to ten minutes is crucial:

“Of course, hopping into your car and gunning it straightaway will put unnecessary strain on your engine. It takes 5 to 15 minutes for your engine to warm up while driving, so take it nice and easy for the first part of your drive.”

Their other big argument against warming up a fuel injected car revolves around that the fuel mixture is more rich when cold, and gas is a solvent that washes away oil, which is true, but ignores the fact that when driving, you’re injecting even more gasoline into the cylinders as you accelerate.

There’s also other safety factors: when your car’s interior is freezing cold, and the steering wheel is so cold it hurts to touch, you’re not going to be driving at your best. You’re distracted, uncomfortable, and can’t manipulate your controls as well as you should.

Plus, there’s often associated visibility issues. Scraping windows is fine, but why not give the car’s defroster a chance to do its job? Those embedded wires get a rear window clear remarkably well, and most modern cars have defrosters that actually work. Give them a chance.

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I’m not talking about idling for an hour here, just five or ten minutes or so at the most. Get up a touch earlier, and make your commute safer and less miserable.

If you’re worried about the environmental impact, consider that you’re also extending the life of your engine and many components inside it when you allow them to get up to something close to a normal operating temperature before you take off, and keeping your car going longer is better for the environment.

(Also, for some people, “warming up” means letting the car sit at idle for like, 20 minutes; no matter what you drive that’s a bad idea, and a clear misconception.)

Plus, an engine at normal operating temperatures is more efficient and pollutes less than a cold one. So I’m thinking that any extra pollutants you’re putting out while idling should be at least partially compensated for by driving on an engine at higher operating temperatures.

So, let’s recap: yes, modern cars can be driven in very cold weather almost immediately following start up. But the idea that there’s zero detrimental impact on the car when you do so is ridiculous.

Your car will operate better when it’s heated up a bit—again, we’re just talking a few minutes, not an hour—you’ll be more comfortable, you’ll drive safer, you’ll see better, and I bet you’ll get a little better-looking.

Seriously, what are you trying to prove, anyway? Nobody will ever love you because your drive right off in cold weather. Take moment and let the car warm up.

It’s worth it. And so are you.

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