Which Is Greener: Idle…or Stop & Restart?

Idling refers to situations in which a vehicle’s engine is running – but the vehicle is stopped.

As we live in the Great White North, most people have grown up with the belief that their car absolutely must be warmed up before driving away.

At one point, it was recommended.

But over the years, vehicle technology has vastly improved – meaning  idling times to warm up a car have changed, too.

Now,  most engines don’t need warming and restarting a vehicle actually uses less fuel and causes less wear and tear on the vehicle’s engine than idling for 10 seconds or more (Taylor, 2003; Ueda et al., 2001; Matsuura et al., 2004).

Contrary to popular belief, idling for more than 10 seconds uses MORE fuel than restarting your engine.

So, if you’re idling more than 10 seconds… turn your vehicle OFF!


Both the US Environmental Protection Agency (EPA, 2004) and Natural Resources Canada (NRC, 2008) recommend idling for no more than 30s–60s.

In general, there are 3 reasons people idle:

  1. idle your car to warm the engine;
  2. idling while waiting for something unrelated to traffic; and
  3. Idle your car in traffic (e.g., at stoplights; in traffic jams).

The first 2 reasons are avoidable , the last …. not so much. 

Idling wastes fuel and money and negatively impacts the environment.

You are literally burning fuel , emitting greenhouse gas emissions – but you aren’t going anywhere!

You can help eliminate unnecessary vehicle idling by turning off your car.

Every time you start the engine, you’re contributing to climate change – the least we can do is ensure we aren’t wasting fuel.

So what IS the best way to warm up a vehicle in the winter?

The answer:

The very best way to warm up your vehicle is to drive it.

Idling is a problem year-round, although it is worse in the winter.

Even on the coldest of winter days (we’re talking -25 degrees!) you should be idling no more than 2 minutes and normally no more than 10-30 seconds.

Wheel bearings, tires and suspension systems will only warm up when the vehicle is moving – but it is a good idea to avoid high speeds and rapid acceleration until all parts are warmed up.

Unfortunately, a series of studies conducted in Canada have suggested that the average individual idles anywhere from 1.4 to 4.6 min a day other than waiting in traffic.

A nationwide telephone survey of Canadian residents, average respondents reported idling for 3.7 minutes per day to warm their engines and 1.9 min a day while waiting in their vehicles (McKenszie-Mohr Associates, 2003).

Here are your take home messages:

  • The average Canadian idles 3.7 minutes per day warming their vehicles and 1.9 minutes per day waiting in their vehicles – which is far above what is recommended (10s – 30s)!
  • Even on the coldest winter days (below -25 degrees) DO NOT idle for more than 2 minutes
  • The best way to warm your vehicle is to drive it
  • The recommended time to turn off your vehicle is after 10 seconds of idling
  • Restarting your vehicle DOES NOT take more gas than turning it off

Thank you Peterborough Mitsubishi for sponsoring this informative blog about idling and being the official vehicle sponsor of Random Acts of Green



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