Issue 40
February 12, 2004

 Any Questions?

Environment Canada's knowledgeable specialists answer questions about wildlife, air pollution, water, weather, climate change and other aspects of the environment.

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From an environmental perspective, when the temperature is extremely cold like -30 °C and below, is it better to idle the car to warm the engine before driving or warm the engine by driving? Is it good to use a block heater? Marc Ballard, Gatineau, Quebec

What are the environmental impacts associated with remote car starters? Lewis Poulin, Montreal, Quebec

When temperatures plummet there is a greater tendency to idle a vehicle engine to let it warm up. Normally, it is considered bad for the environment to allow a vehicle to idle because fuel consumption is increased as the engine is burning fuel but not moving, releasing greater emissions into the air.

However, the impact of cold weather on vehicle engines involves a number of issues. Letting the engine idle for a few minutes after a cold start up can reduce some exhaust emissions. By allowing the engine to warm up, it will use less fuel when operating at higher RPM and under load than when cold.

Researchers from the Environment Canada's Environmental Technology Centre have tested several vehicle models under cold conditions. After a cold start at -18 °C, a 1993 Buick Regal with a 3.8 V6 engine showed that when the engine was idled for five minutes and 10 minutes before putting the car in gear and driving, the regulated exhaust emissions of total hydrocarbons, carbon monoxide and oxides of nitrogen were reduced over a simulated urban driving cycle.

In each condition, the vehicle had been parked in -18 °C temperature for at least 10 hours. Researchers also measured carbon dioxide (CO₂) emissions while the vehicle was idling. When the engine was left idling for a five minute period the CO₂ increased by seven per cent for the total trip. This increased to 12 per cent with the 10 minute idle interval.

A second smaller vehicle, a 1996 Sunbird powered by a 2.2 litre engine was tested under the same conditions. It revealed increases in CO₂ of 14 per cent after the five minute idle and 19 per cent after the 10 minute idle. The regulated exhaust emissions results were mixed with some emissions being increased and others decreased.

Finally, a sub compact car powered by a 1.3 litre engine was tested. The results indicated reductions in the regulated exhaust emissions but had CO₂ increases of 14 per cent and 19 per cent respectively for the five and 10 minute idle periods.

Under colder temperatures, the impact on fuel consumption is greater as there is increased friction on all moving parts and more fuel will be required for combustion until the engine is warmed up. At extreme cold temperatures, idling the engine for a period of time is also important in order for the mechanical components to warm-up prior to subjecting them to the stresses related to normal driving.

Block Heaters

Block heaters are primarily used for starting purposes at colder temperatures and can greatly decrease the warmup time of the engine and the idling time that should be used. With the blockheater, less fuel is required to start the engine as the engine block is pre-warmed. Block heaters need only be on between 1 to 2 hours to be effective. When considering greenhouse gas emissions, the source of the electricity must be taken into account as coal or oil combustion power generation result in greater CO₂ releases.

In a test program conducted by the Environmental Technology Centre, a vehicle sitting at -25 °C was warmed using a block heater for two hours and then driven over the simulated urban driving cycle. This resulted in a 25 per cent improvement in fuel consumption compared to cold-starting a vehicle and driving it over the same route.

Remote Starters

As idling a vehicle engine in cold weather for more than a few minutes will result in increases in greenhouse gases, the use of remote starters will, in the majority of cases, also lead to greater GHG emissions. Unfortunately, many people use a remote starter to warm-up the engine to the point where the car heater is warming up the interior of the vehicle and defrosting the windshield. On very cold days this could take upwards of 10 to 15 minutes, depending upon the age of the vehicle.

When possible, pre-warm your vehicle using a block heater and reduce your car idling to no more than 2 – 3 minutes. This is sufficient time to warm the engine and to ensure that the working components are not under stress. Of course, driving less or opting for public transit is the best way to reduce damaging GHG emissions.

Related Links:

Testing Vehicle Emissions in Canada

Transportation and the environment

Smog Fact Sheet

Reducing Smog