Idling: Myths Versus Reality

Ask Canadian motorists why they idle their vehicles, and you'll likely get a simple answer: to warm up the engine before they drive away. It's one of the most commonly held myths in Canada about driving. And it costs you money, wears out your vehicle's engine and generates unnecessary greenhouse gas emissions that contribute to climate change.

Contrary to popular belief, idling isn't an effective way to warm up your vehicle, even in cold weather. The best way to warm it up is to drive it. In fact, with today's engines, you need no more than 30 seconds of idling on winter days before you start to drive.

The notion that idling is good for your vehicle is pass̩ Рin fact, it hasn't been the right thing to do since the advent of electronic engines. The truth is that excessive idling can damage the engine.

The reason? An idling engine isn't operating at its peak temperature, which means that fuel doesn't undergo complete combustion. This leaves fuel residues that can condense on cylinder walls, where they can contaminate oil and damage parts of the engine. For example, fuel residues are often deposited on spark plugs. As you spend more time idling, the average temperature of the spark plug drops. This makes the plug get dirty more quickly, which can increase fuel consumption by 4 to 5 percent. Excessive idling also lets water condense in the vehicle's exhaust. This can lead to corrosion and reduce the life of the exhaust system.

Besides, what's often forgotten is that idling warms only the engine – not the wheel bearings, steering, suspension, transmission and tires. These parts also need to be warmed up, and the only way to do that is to drive the vehicle.

Perhaps you're concerned that continually shutting off and restarting the vehicle is hard on the engine. But studies show that frequent restarting has little impact on engine parts such as the battery and starter motor. The wear on components that restarting the engine causes adds about $10 a year to the cost of driving – money that you'll likely recover several times over in fuel savings from reduced idling.

So, when should you turn off the engine? Believe it or not, more than 10 seconds of idling uses more fuel than restarting the engine. As a rule of thumb, if you're going to stop for 10 seconds or more – except in traffic – turn the engine off. You'll save money. And your vehicle won't produce harmful emissions of carbon dioxide, the principal greenhouse gas that contributes to climate change.