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Do I Really Need to Let My Toyota Idle Before Driving in Winter?

Posted at Fri, Feb 26, 2021 9:00 AM

Those of us that live in colder climes are more than familiar with all the ways winter can impede driving, as well as create a number of inconveniences related to owning a vehicle. Most of us have probably been told that when starting our vehicles during the coldest days, we need to let the vehicle idle for a while before we drive it. Whether or not this particular bit of advice is actually beneficial is up for debate, but in order to provide Long Island Toyota drivers with the right knowledge, we here at Westbury Toyota have gathered all the evidence needed to dispel this myth.

Why the Belief That Vehicles Need to Idle In the Cold?

This widely held falsehood actually started with a nugget of truth at its core, explains Chris Mooney of The Washington Post: Fuel economy falls when the temperatures fall to extremes, and it does take longer for the engine and all the related parts to heat up to an optimal range when driving on the coldest days. At one point in time, it was advised to let the car warm up, but things have changed since them.

To get a better idea of how this myth came about, it helps to be able to understand just how everything works. Internal combustion engines function by mixing air and gasoline inside their cylinders. That mixture is then compressed and ignited by spark plugs, which gets the pistons moving. In older cars (pre-1980s), the carburetor was in control of mixing air and fuel. However, carburetors were not able to precisely control the amount of fuel in the mixture, and because gasoline does not evaporate well in cold weather, the carburetor often wound up mixing in more fuel than was needed. The mixture, now gasoline heavy, led to an increased chance of engine damage once it was ignited by the sparkplugs. To try and lessen the chance of engine damage, people were advised to idle their vehicles for a few minutes during the coldest days to let the engine heat up. Once the engine was warm, it was easier for the carburetor to add the right amount of fuel to the mixture.

Why Is Warming Your Car up No Longer Necessary?

Later on in the 80s and early 90s, automakers advanced from carburetors to a more sophisticated, accurate system: Electric fuel injectors. Cars with fuel injectors have sensors that keep track of the ambient temperature outside, and the system will accordingly adjust the fuel-air mixture based on that temperature. If it is very cold, the fuel injector will create a mixture that is fuel heavy by adding more gasoline, which makes up for the low levels of evaporation. If your Toyota has electric fuel injectors, letting it warm up for ten minutes every morning during the winter is not doing much good other than to heat up the interior and defrost your windshield. If you let it idle for longer than three or four minutes, all you are really doing is wasting fuel.

Is Letting Your Car Idle on Cold Days Actually Harmful?

The answer is yes, in a couple of different ways. First of all, idling your car unnecessarily counts as wear and tear on your engine. What’s more, the gasoline that does not evaporate can mix with the engine’s lubricating oil and decrease its lubrication efficiency, which in turn leads to metal on metal friction.

The other way that idling your car can be detrimental is in the fumes that your car releases during the idling period. These fumes add to greenhouse gases, and while it may seem like your Toyota is not much of a contributor in that regard even if you do let it idle, remember the millions of other North Americans that also do the same. The result is an astronomical amount of unnecessary greenhouse gas emissions.

Don’t Run Your Toyota for Several Minutes Every Day

While it is always a good idea to ensure your car, truck, van, or SUV runs long enough on a cold day to get the window defrosted, that is really only as long as it should idle for. Unless your Toyota still has a carburetor (which means it is probably quite old!) there is no reason to idle for more than three to four minutes when you start it up in a cold snap. By idling it for only a short while, you are ensuring that you are not wasting fuel, putting needless strain on your engine, and reducing the amount of harmful emissions.

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