Warming Up Your Car in the Winter

Most people operate under the assumption that they have to warm up their engines in cold weather. The idea is that by warming up your car, it will run better since it has a chance to idle for 10-15 minutes before driving. Older drivers swear by this practice – but, is it true? Do you need to warm your car’s engine before driving? Let’s take a look at the facts and get to the bottom of this much-debated practice.


The Role of the Thermostat

Before we move ahead, you need to understand the function of a car’s thermostat.

A thermostat is a small, yet important device that sits between the radiator and the engine of a car in liquid-cooled engines. Its job is to block the coolant flow to the radiator until the engine warms up. Once the engine hits a certain temperature, it opens and allows the coolant through so that the car does not overheat.

The important point here is that there is no flow of coolant through the engine when it is cold. While the primary purpose of coolant is to keep the engine from overheating, it does perform other tasks. Coolant reduces deposits, emissions and engine wear.


Round #1 Goes to “Warm Up Your Car.”

When the air temperature and the engine are cold, you do NOT need coolant flowing through your engine to keep it cool. However, coolant does serve other secondary purposes.


Keep the Liquids Flowing – Idling and Oil Circulation

We hope you have never had an engine seize on you – what an awful, gut-wrenching experience. Motor oil has to circulate for the engine to run. The oil reduces friction between all the moving metal parts inside the engine. Until the engine warms the oil, it is thicker and harder to move. Liken it to a human heart. When the blood is thicker, the heart has to work harder to pump it through the body. Similarly, the oil pump must work harder to move the oil through the engine. Parts move less freely, and motor wear can occur.


Round #2 Goes to “Warm Up Your Car.”

Idling your car and warming the engine also warms the oil. Parts move freely, and there is less stress on your car at higher speeds.


Idling Your Car Accomplishes Little and Wastes Money

The Environmental Defense Fund states that if you are going to stop for more than 10 seconds, then turn off the ignition.

“After ten seconds you waste more money by running the engine than restarting it.”  – Andy Darrell, Deputy Director, EDF Energy Program

Switching the car off when you can leads to extra cash in your pocket, and it will also protect your community from additional air pollution.  The efficiency of modern fuel injection, which eliminated carburetors and chokes, reduces the need to idle your car.


Round #3 Goes to “Don’t Warm Up Your Car.”

The only reason to let a car idle is to allow the engine oil to circulate, but only 3 seconds is necessary according to the Minneapolis anti-idling ordinance.


There Are No Benefits to Idling Modern Cars

There are no benefits to idling modern cars for long periods of time in the winter.  Doing so can potentially damage the engine and its components, including the spark plugs, the exhaust system, and the cylinders.  In today’s modern vehicles, the electronic fuel injection system regulates the amount of fuel that the engine needs to run efficiently.  When the engine is cold, the fuel injectors send more fuel through the system.


Round #4 Goes to “Don’t Warm Up Your Car.”

As the engine warms up, it needs less fuel to produce better performance.  So, the longer that you let a car sit idle, the more fuel you’ll waste which leads to poor engine performance as well as a reduction in mileage.


Driving Warms the Engine Faster Than Idling

Bob Aldrich, the retired webmaster of the California Energy Commission, said that “idling is not an effective way to warm up a car – it warms up faster if you just drive it.”

If the engine of a car is running at an idle state, then it’s not doing any work.  If you put a load on the car and drive it, then it will help to produce heat faster.  Modern electronic engines do not need to warm up, even in the season of winter.


Round #5 Goes to “Don’t Warm Up Your Car.”

The best way to warm the engine of modern cars is by easing into your drive and avoiding excessive engine revving.  The car’s engine warms up faster when driven compared to just idling.


Block Heaters – The Solution to the Problem

Remote starters have become popular for a number of reasons, but their main purpose is to warm up a vehicle before driving. However, the car still sits idling in the driveway – which we’ve determined may or may not be a good thing.

Block heaters could be the answer to the debate on whether to “warm” or “not warm” the vehicle. Block heaters provide the benefits of idling without the negatives.

Block heaters are designed to heat the engine and only cost $50 or less, depending on the company and model.  These block heaters work on a timer that can be set to begin warming the engine from one to two hours before driving the car in very cold climates. In other words – you can heat your car without starting the engine.


The Verdict is That “It’s a Draw.”

After reviewing the arguments and the facts involved, it appears that both sides of the debate can present valid points. There are benefits to idling older cars and warming the engine. There are also drawbacks to doing so. Using a block heater allows you to preserve the benefits of warming your engine without compromise.







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