Should you warm up your car before driving?

Can you drive your gas-powered car when it hasn’t been warmed? Does idling for five minutes warm up the cabin? Is a block heater at all useful? We’ll answer these questions and more about warming up your vehicle in the winter.

Engine basics

To understand engine basics, let’s first look at Jell-O, a mixture of water, gelatin, sugar, and food colouring.

Nothing happens when you first add the package’s contents to room-temperature water. However, after you heat the mixture, it thickens. Once you’ve poured the thickened mixture into a bowl and set it in the fridge, it cools and becomes the bouncy dessert so many people enjoy.

In other words, temperature plays an important role in the making of Jell-O.

The fluids that run through your car’s internal combustion engine (ICE) have similar properties.

If their temperature dips low enough, these fluids thicken and increase friction as they flow through your engine. This means your engine must work harder to provide power to your vehicle. Fluids that have reached their optimal temperatures will flow smoothly through your engine, improving fuel efficiency.

Batteries perform in a similar fashion. Because they rely on an electric-chemical reaction to manage their energy, these reactions slow down in the winter.

Despite these updates in automotive technology from the past two or three decades, myths about warming up your engine still abound. Let’s look at some important ones.

Myths about warming up your engine

Although you need to warm up your engine to improve fuel efficiency, “warming up” no longer means what it meant years ago. Let’s look at a few myths and realities of about warming up your vehicle today.

Myth #1: Idling warms up the engine

This procedure comes from the days of vehicles with carburetors, when very cold engines performed so poorly that the car would sometimes not start until the carburetor warmed up. However, carburetors were phased out in the 1990s.

As fuel-injection engines became the norm, some idling to warm up the engine was recommended. The Government of Canada, for example, recommended idle for two or three minutes about 15 years ago.

However, you get no mileage from idling, which no longer sufficiently warms up your engine.

Reality: Turn on your vehicle no more than 30 seconds before you plan to drive.

Myth #2: Idling warms up the windshield

Vehicles heat their cabin with the extra heat produced by engines. Therefore, warm air won’t blow out of the vents when you first turn on your car because the engine is cold. And since you can’t warm up an engine today through idling, you can’t rely on your heating system’s defrost mode to help you scrape off that pesky ice.

Reality: If you’re expecting a chilly night, keep your vehicle covered. Conversely, purchase de-icer to help clear your windshield. Do not use hot water to melt the ice; your windshield may crack.

Myth #3: Idling to warm up the engine doesn’t use any gas

Your engine actually uses gas when it’s idling. But without driving the car, your engine can’t create heat.

Reality: Idling wastes gas but gets you nowhere. This decreases fuel efficiency.

What about a cold start? We share the myths and realities of cold starts here.

Getting your car ready for a winter drive

So, if idling no longer warms up your vehicle, how do you get ready for your drive?

• Turn on a block heater about two hours before you plan to drive if you live in a location with frigid winters.
• Park in a warmer spot, like a garage.
• To make removing ice easier in the morning, cover your windshield—or your whole vehicle—at night.

If you want specialized advice for your vehicle, or if you believe you’re having extra difficulties getting your vehicle started after a cold night, visit your local NAPA AUTOPRO service centre, and one of our experienced technicians will be happy to help you out.