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Since modern cars have fuel-injection systems their engined don’t need to be warmed up. (Stefan Redel, sredel@sredel.de/iStockphoto / Getty Images)
Since modern cars have fuel-injection systems their engined don’t need to be warmed up. (Stefan Redel, sredel@sredel.de/iStockphoto / Getty Images)


The myth about warming up your car on a cold day Add to ...

The Stegosaurus disappeared more than 100 million years ago, doomed by its tiny brain and a changing world. Then we come to the carburetor, a crude fuel-mixing device that once ruled the automotive universe.

Today, the carburetor is largely extinct, kicked aside by the modern fuel-injection system. Yet millions of drivers still seem to be stuck in the Jurassic Period. I thought of this recently when I watched a man spend 10 minutes warming up a fuel-injected Toyota that could have been driven seconds after it was started.

Few processes are as poorly understood as the cold-weather start. Back in the days of carburetion, a car couldn’t be driven until it was warmed up. Today, warming-up is a counterproductive exercise that wastes fuel, harms the environment and damages your car. Let’s have a look at the science, history and flawed folklore behind the automotive warm-up:

Virtually every car on the market today is equipped with a fuel-injection system that adjusts gasoline delivery based on temperature, throttle setting and engine load – because of this, your car can be driven almost immediately, even at low temperatures.

Even in extremely low temperatures, most fuel-injected cars can be driven away less than 30 seconds after start-up. The best way to warm an engine is to drive away as soon as possible and keep the load low until it reaches ideal operating temperature. Accelerate gently and use small throttle openings. Driving loads the engine and warms it more quickly than extended idling.

Engines are most efficient when they operate in their optimum temperature range. Running an engine when it’s cold causes increased emissions and engine wear. The goal is to get the engine into its preferred temperature range quickly.

Using a block heater can dramatically reduce the wear on your engine by improving oil flow on initial start-up. According to tests by Environment Canada, a block heater can improve overall fuel economy by as much as 10 per cent – you get zero miles per litre while idling and fuel economy is best at optimum engine temperature, so you should reach the target zone as quickly as possible. Environment Canada tests also showed that warming up an engine with extended idling leads to sharply increased emissions.

Although driving away as soon as possible is optimum, you may be limited by visibility requirements – the defroster system in your car won’t work until the engine generates enough heat. This can be offset by the use of a plug-in interior heater. Some manufacturers offer windshields with embedded heating elements, which speed defrosting.

The science and engineering that govern engine performance are relatively simple. Metal parts expand and contract with temperature and are designed to work best within a specific range. The efficiency of fuel combustion also varies with temperature – a cold engine burns extra fuel.

The catalytic converter unit installed in your car’s exhaust system is less efficient when it’s cold. This is another reason why short warm-up times reduce emissions.

Many drivers base their warm-up practices on outmoded technology and outdated thinking. When cars had carburetors, engine warm-up was essential – trying to drive a carbureted car when it was cold was like waking up a temperamental senior citizen from a deep sleep. Modern fuel injection systems automatically adjust themselves to deliver the correct amount of fuel, and are ready to go almost immediately.

Extended-idle warm-ups were once encouraged due to lubrication technology. Old-school oils didn’t work well in low temperatures. Modern synthetic oils can flow well at temperatures as low as - 40 C.

Use remote starters wisely. Many drivers start their engines far ahead of time so their car will be toasty warm when they get in. This extended idle has a high cost. According to the Oak Ridge National Laboratory (a division of the U.S. Department of Energy), excessive idling shortens the life of your exhaust system and spark plugs because a cold engine creates more damaging combustion byproducts than a warm engine. Carbon and soot buildup also reduces the effective lifespan of engine oil.

Read more questions and answers from Peter Cheney and Globe Drive here

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