Idle the Car or Switch It Off? Answers Here!
Yes, it’s a long time since I learnt to drive. Then, I was told that:
- You need to idle the car before starting to drive, particularly in cold weather
- It’s better to leave your car running (idling) if you’re stopping for a while, because it uses more fuel to stop and re-start a car, than it does to leave it running, or idling.
But that advice is no longer accurate!
It may have been true in the ‘dim and distant past’ but it certainly isn’t true nowadays with our modern cars.
- Idling your car simply uses fuel and costs you money, while also spewing pollutants into the air.
- Starting a car’s engine uses only a negligible amount of fuel and doesn’t have a massive impact on the wear and tear of the engine.
OK, but if you no longer need to idle your car, that means 2 questions:
- Don’t you need to idle your car to warm it up in cold weather before you start driving?
- If you’re stopping for a short while, is it better to switch off the engine or to idle the car?
Here’s what you need to know.
Should You Idle the Car to Warm It Up in Cold Weather?
What about warming up a car, especially in cold winter weather? Doesn’t the car need time to warm up before you can safely drive it?
Cars should be warmed up – but idling is not the way to do it, not even in cold weather!
The best way to warm up your car is to drive it. You need no more than 30 seconds of idling before driving away, even on the coldest days. Just avoid high speeds and rapid acceleration for the first 3 miles / 5km.
The catalytic converter – the device that reduces pollutants from the vehicle exhaust – doesn’t function properly when it’s cold, and the best way to warm it is to drive the car. You emit more pollution if the catalytic converter is cold.
The tyres, transmission, wheel bearings and other moving parts also need to be warm for the vehicle to perform well. Most of these parts do not warm up until the vehicle is driven.
Summary: drive your car straight away in cold weather to protect both the car and the environment. But take it easy for the first few miles while the car warms up.
Related: What about idling in diesel and hybrid cars? Is it different for them? Also, which technology is available in Europe and Asia, but not in the US!
When Stopping For a Short Time, Should You Idle The Car or Switch Off?
What is the cut-off point now – in other words, at what point does it make sense to idle the car rather than switch it off?.
In a modern car, it’s 10 seconds.
10 seconds? Is that all?
So if you’re stopping for more than 10 seconds, you should switch off the engine.
But of course, 10 seconds isn’t always practical – for example in traffic. Use common sense to work out if it makes sense to switch off or to idle the car at these common idling spots:
- drive-through service lines,
- rail crossings,
- car wash queues,
- carpool lines,
- departure from concerts and sporting events,
- while talking to friends
- while using the cell phone.
By understanding the effects of idling and reducing the practice, you can improve your car’s performance, save money, and reduce pollution.
Is It Bad To Idle The Car?
Interestingly, excessive idling can actually damage your engine components. An idling engine is not operating at its peak temperature, which means that fuel does not undergo complete combustion. This leaves fuel residue that damages engine parts and can contaminate oil.
To end, here’s a very useful thing to remember:
An idling car is the most inefficient car on the road — it gets zero miles per gallon
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Editor’s Note: This article has been updated with more current information