By Jim Kerr

Winter weather means warming up your vehicle before driving. The question is how long should you let it warm up? Does idling harm your vehicle or help prolong its life? The facts might surprise you.

One fact is easily discernable – idling uses fuel. Your fuel economy is zero because the vehicle isn’t moving. The less time spent idling or warming up the engine, the less fuel used, meaning more money in your pocket. According to research done by Natural Resources Canada, we idle our vehicles an average of five to 10 minutes every day. During the peak of winter, idle time is much more than in summer, with all Canadians idling their vehicles for a total of 75 million minutes a day. If we were to reduce the time each vehicle idles by five minutes, we would save 680 million litres of fuel. At a $1.00 per litre, that adds up to $680 million dollars a year we could keep in our pockets rather than spend it on fuel.

Idling costs money in other ways too. When an engine is idling, it never warms up completely to operating temperature like it would when we drive. Acids and moisture that are formed in the engine by the combustion process do not evaporate out of the engine oil until the oil is fully warmed. These contaminants contribute to increased engine wear, more sludge formation in the engine oil and deposits formed on engine valves. The deposits on valves hinders fuel flow through the intake ports, so fuel economy drops even further.

Internal engine friction is a huge waste of fuel. Keeping parts lubricated adequately is one method of reducing this friction, but some engine parts depend on splash or spray to receive lubrication. Many V8 engine camshafts are lubricated by splash. Most engine cylinder walls are lubricated by splash. When an engine is idling, these parts receive less lubrication because the speed of the crankshaft isn’t fast enough to splash ample oil onto the parts. Idling can wear parts faster than when driving.

Replacement exhaust systems are expensive. Vehicles that are driven long distances require less exhaust work because the moisture inside the mufflers and pipes gets hot enough to evaporate out. When an engine idles, the exhaust gases are cool, so the moisture collects inside the exhaust system and rusts it from the inside out. Avoid idling and short trips and your exhaust system will last much longer.

There are times when we need to idle a vehicle. If the windows are frosted over, then we need to have the engine warm enough to provide clear visibility. Using a block heater helps. At -20C, a block heater can improve fuel economy by 10% because cold engines use much more fuel during start-up. The block heater only needs to be on for a couple hours, so adding a timer on the block heater cord will save on electricity too. A bonus of using a block heater is faster windshield defrosting and interior heating.

The engine really only needs about 30 seconds of idling time to get oil moving to all parts. After that, the vehicle is warmed up better by driving it. Avoid high rpm or hard acceleration, but otherwise drive it normally. By driving the vehicle you are warming up the transmission, drive axle, tires, steering, suspension and wheel bearings. None of these parts warm up just by idling the engine, so your vehicle will actually last longer if all parts are warmed up at the same time.

Turning off the engine when you are parked also saves money. Research by Natural Resources Canada shows that it is more efficient to turn off the engine and restart it again if you are going to be parked for more than 10 seconds. The cost of restarting the engine is estimated at about $10 a year using this technique and the savings in fuel costs will far more than offset this. Hybrid vehicles use this technique to save up to 15% in fuel costs. While their programming allows engine stops even when sitting at a traffic light, it is more practical for conventional vehicles to keep the engine idling at a stop light. However, if you had to wait for a train crossing or are parked and waiting for a passenger for more than 10 seconds, it is more efficient to turn it off.

Idle time is great for a person to relax and perhaps read a good book. Idle time for an engine isn’t good. Save your money and your vehicle by keeping idle time to a minimum.

Connect with