Do modern cars need to be warmed up?

Our parents taught us that you need to let your car warm up before you drive it, but is this true? Or are you just wasting fuel?

If you were around 20–30 years ago, you’d remember either starting the car or watching your parents start it and letting it idle for a few minutes before driving it.

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There is conflicting information about why people do this. Some say it’s to oil the engine, while others can’t even answer the question; they just know they’ve been told to warm it up.

Do I need to warm my car up?

Unless you own an old car, your car has been sitting for a while, or your windows are foggy, no.

Modern cars are very different to those of years past. Modern fuelling solutions and accelerated oil development mean that sitting and leaving the car idling for a few minutes has been rendered obsolete.

“Oil has become more technologically advanced and is now much more efficient,” says James Boer, who has been a Bentley and Rolls-Royce mechanic for five years.

“It doesn’t break down over hot and cold temperatures, the viscosity stays the same, and it circulates through the engine much more efficiently.

“When it comes to modern-day fuelling, there are a heap more sensors on the engine that let the computer know the optimum fuel/air mixture.”

Old cars used to supply fuel to the engine through an entirely mechanical process.

When the car was cold, you could apply something called a ‘choke’ to change the ratio of air and fuel in the engine, and this would make it warm up faster and run at a higher RPM.

New cars use something called electronic fuel injection, which sees a little computer in the car do a bunch of calculations with the help of all the sensors on the engine to find the best air-to-fuel ratio on a cold start.

This is why your car will run at a higher RPM when it is cold because the computer is trying to warm the engine up faster.

With modern oil and oil pumps in your engine, you really don’t need more than a few seconds to start driving. The oil will almost instantly circulate through the engine, and our climate typically doesn’t get cold enough to affect the oil temperature or freeze the water in the engine.

“You wouldn’t sit there letting a modern car idle, but you also wouldn’t pin the throttle to the floor while it is still cold. The oil still needs time to circulate the engine, and the computer still needs to get to the optimum air-fuel ratio,” Mr Boer explains.

“The only time I would feel the need to warm a car up is if it has been sitting for a week or longer, just to let the oil circulate.”

How much fuel are you wasting by idling?

Let’s say, on average, that each time you head to work in the morning and then when you get in the car to go home, you let the car warm up for five minutes.

Let’s say that’s 10 minutes of idle time per day, five days a week, 52 weeks a year. That’s 2600 minutes a year or 43.3 hours.

Studies have shown that idling engines use around 0.6L/hour per litre of engine size. That equates to 26 litres of fuel wasted per litre of displacement per year.

If you had a 2.0-litre engine, you are essentially kissing away 52 litres or around $105 worth of fuel just sitting there.

Just drive the car calmly when you first start and you won’t have to worry about wasting fuel and time. The car will warm up much faster under running load anyway. 

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