Are you the driver who lets the car run for five to ten minutes before you leave in the morning? Or maybe you are the driver who gets disapproving looks from your passengers when you drive off as soon as you start the engine? No matter which end of this dilemma you are on, read on to find out the facts about warming up your car before driving.
The Logic Behind Warming Up
The practice of idling your car in winter has been around for a very long time. And it does make sense when you think about it: cars do take longer to warm up and get worse fuel economy in cold weather. The idea behind it is that idling before driving is necessary to:
- allow the oil to circulate through all parts of the engine
- let the engine reach its normal operating temperature
- reduce engine wear and prolong its life
These reasons sound convincing and it’s understandable why someone without mechanical knowledge can take them for truth. Some die-hard supporters of this practice would let the car idle anywhere between five and ten minutes before driving off. Another approach is to wait till the temperature indicator moves half-way between C and H, which could take even longer on some vehicles.
The Facts Behind Warming Up
It’s important to understand that “warming up” your vehicle in the morning doesn’t require idling. All modern vehicles were designed with cold weather in mind and can warm up just fine while in motion.
- Driving your car will allow all of the components to warm up faster than idling.
- Prolonged idling may damage the engine and its components due to incomplete fuel combustion.
- Prolonged idling may lead to the early failure of the catalytic converter due to its inefficient performance during idling.
- Idling contributes to the pollution more than driving as it releases more unburnt gasses.
- Warming up your car wastes gas and money, especially if your vehicle uses premium fuel.
- Idling your car inside a garage may cause dangerous fumes to enter your home.
- Leaving your car unattended while idling opens up an opportunity for theft.
- Cars built in the last 20 years only need no more than 30 seconds of warm-up time, regardless of whether the engine runs on diesel or gasoline.
In fact, Maryland Transportation Code has an anti-idling provision that imposes a fine of up to $500 for idling a vehicle for longer than five minutes. There are exceptions that allow longer idling and “bringing vehicle to manufacturer’s recommended operating temperature” is one of them. Check with you car’s manual to see what your manufacturer recommends, but the chances are good that little to no idling time is required.
What You Should Do Instead
You don’t have to wait to drive longer than 30 seconds after starting your car. However, for the first five to ten minutes, drive the car gently, with smooth braking and acceleration, to avoid putting unnecessary stress on the engine. Keep the RPMs low and don’t slam on the brakes—this is enough to allow your car to warm up while in motion.
You could let it idle a bit longer if:
- The temperature is far below freezing
- You need to clear large amounts of snow or ice off your car
- You want the interior to get toasty warm when you get in.
Generally, once your windows are defrosted and you have all-around visibility, you are good to go. And while the car might feel cold initially, the interior will get warm faster when you are driving. Turn the heat on low when you start the car, so that you don’t get a blast of cold air in your face. Turn it up once the air gets warm. To save gas, you can get an external car interior preheater or make sure your next vehicle operates heat independently of the engine like some hybrid and electric cars.
Unless your car dates from the 1980s, there is no reason to shiver in your car waiting for the engine to warm up. Cars from that era had carburetors, which twist open a small plate to suck air and fuel through a tube and into the engine.
But if the carburetor is too cold, it doesn’t work the way it should. That can change the ratio of gas to air — too much air and not enough fuel, or vice versa — causing the car to seize up or run smoky. And that, as you can imagine, isn’t all that good for it.
These two ingredients mix above a car’s pistons (those hardworking, moving parts you might more commonly observe on the wheels of an old steam engine). There the mix is compressed by an upward stroke of the piston before being ignited and forcibly pushing the piston back down. The result: mechanized motion.