Speeding up the Heat on a Chilly Morning

Dear Car Talk

Dear Car Talk | May 24, 2018

Dear Car Talk:

I have a car-related question that's been bothering me for a while. I was born and raised in a place where heat was far more of an issue than cold, so I grew up learning that at high temperatures, using the heater for the passenger compartment could be used to cool the engine if it started heating up too much.

Now that I've moved to a place where it snows, I'm being told that when it's cold, using the heater actually will warm the car faster, because the thermostat will request more heat from the engine, causing it to come up to temperature faster. True? Thanks! -- Patrick

False. You're welcome.

The first part is true. The heater is, essentially, a smaller radiator that lives behind your dashboard. And when you turn it on, you draw heat away from the engine and into the passenger compartment.

If the engine is starting to overheat, adding even a small extra radiator will help cool the engine -- even if it ends up melting your Crocs.

But contrary to your wishful thinking, Patrick, drawing heat away from the engine will not make the engine warm up any faster. There's no "switch" or "thermostat after-burner" setting that commands the engine to warm up faster if you ask for heat. It's always warming up as quickly as it can.

So if your primary goal in life is to get heat as quickly as possible, your best bet would be to start the engine and, with the heat off, drive away immediately (driving warms up the engine faster than idling). And then check after a couple of minutes. When the air coming out of the vents is no longer colder than the air in the car, leave the heat on. Or, if you're lucky enough to have a temperature gauge on your dashboard, then just turn on the heat as soon as the temperature needle moves at all.

By the way, most cars that have climate control do this for you automatically. They'll let the engine start to warm up and wait until there is heat before they start blowing any kind of air on you.

Now, once you turn on the heat, you'll cause the engine to take a little longer to get to its full operating temperature. But when your frozen butt cheeks are teetering on the folds of your rock-hard leather seats, who cares about the engine?

It's true, the engine won't run at its most efficient until it reaches full operating temperature, but you won't harm your engine by delaying its warmup a little bit -- especially if you're driving it gently.

After all, you're an American, Patrick. And as such, you are entitled to life, liberty, the pursuit of happiness, and automotive heat at its first available moment. Claim those rights.

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