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Vehicle Warm-Up

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 about driving in Canada. Excessively long warm-ups cost you money, waste fuel and generate unnecessary greenhouse gas emissions that contribute to climate change.

To assess the impact of vehicle warm-up, Environment Canada conducted a test program using a cold chamber and three vehicles. Each vehicle was cooled to -18°C and driven over a simulated urban driving cycle. The test procedure was performed using a 5-minute warm-up before driving the simulation urban cycle and repeated using a 10-minute warm-up before driving the simulated urban cycle.

The test results showed that with a 5-minute warm-up total fuel consumption increased by 7 to 14 percent and with a 10-minute warm-up total fuel consumption increased by 12 to 19 percent7. This also leads to a similar increase in carbon dioxide (CO2) emissions, as they are an unavoidable by-product of burning fossil fuels.

Contrary to popular belief, excessive idling is not 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 computer-controlled engines, even on cold winter days, usually no more than two to three minutes of idling is enough warm-up time needed for the average vehicle before starting to drive – but make sure that windows are free from snow and properly defrosted before driving away!

Please consult your owner's manual or your vehicle service advisor if you would like a recommendation specific to your vehicle or climatic conditions.

Unfortunately, some motorists warm up the engine to the point where the car heater has warmed the interior of the vehicle. On cold days, this could take upwards of 10 minutes and, as can be seen from the tests, will have a significant impact on fuel consumption and emissions of carbon dioxide (CO2), the principle greenhouse gas.

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. Until the engine temperature begins to rise, it's a good idea to avoid high speeds and rapid acceleration. It's also important to ensure that windows are free from snow and properly defrosted before driving away!

Give your car a helping hand in winter and consider using a block heater

You will use more fuel and create more CAC and GHG emissions in the first minutes after a “cold start” than when the engine reaches normal operating temperatures. When an engine starts up, it pumps oil throughout the engine block to lubricate moving parts. In a cold engine, the oil is thick and resists flow, so the engine has to work harder to overcome internal friction.

Fuel combustion is also less efficient in a cold engine, and the air-fuel mixture is richer - in other words, there is more fuel and less air in the mixture. (The mixture of fuel vapour and air must be in proper proportion for efficient combustion.) The combined effect is a sharp increase in GHG and CAC emissions. On top of everything else, the catalytic converter doesn't work efficiently when it is cold. Therefore it is important to drive the vehicle so that it reaches its proper operating temperature as soon as possible in order to maximize fuel efficiency and reduce emissions.

On cold winter days you can help to reduce the impact of starting your vehicle by using a block heater. This device warms the coolant, which in turn warms the engine block and lubricants. The engine will start more easily and reach its operating temperature faster. This can greatly decrease the amount of idling warm-up time of the engine and allow the engine to reach its proper operating temperature faster.

At -20°C, the use of a block heater can improve overall fuel economy by as much as 10 percent. In a test program conducted by Environment Canada, a vehicle sitting at -25°C was warmed using a block heater and then driven over a simulated urban driving cycle. This resulted in a 25 percent reduction in fuel consumption compared to cold-starting the vehicle and driving it over the same route.8

A block heater runs on electricity. To save money, invest in an automatic timer that switches the block heater on two hours before you plan to drive the vehicle (instead of leaving it plugged in all night). Usually this is all the time needed to warm the coolant and the engine.

Extra winter tips

Given the test results, it is important to use remote car starters wisely and reduce unnecessary warm-up time. And remember, combining trips in cold weather can save you even more fuel and money in the winter months by saving the extra fuel required to warm up a vehicle.

7 It should be noted that the Environment Canada test results did not show a clear trend with respect to the regulated exhaust emissions of hydrocarbons (HC), carbon monoxide (CO) and oxides of nitrogen (NOx). Environment Canada (EnviroZine On-line Newsmagazine). Retrieved April 2008.

8 Environment Canada (EnviroZine On-line Newsmagazine) Retrieved April 2008.