It is a common practice to let your engine idle to warm it up, especially on cold mornings. Did you know that some people also let their engine idle all day? Many people who work in oil fields and on farms use their trucks to tow equipment that they need for their work. So, they leave their trucks idling when not in use, because they think it increases the engine’s performance and towing capability. 

Whether you let your engine warm up for 10 minutes or idle it for 10 hours, you’re damaging it. Why? Because newer engines are made for motion, not to sit and idle. We have heard a lot of reasons why our customers continue with this practice even after their engines have failed due to excessive idling, so let’s address a few of them.

But my dad always said to warm up my engine!

Warming up your vehicle before driving is a leftover practice from a time when carbureted engines dominated the roads. Carburetors mix gasoline and air to make vaporized fuel to run an engine. However, they did not have sensors that tweak the amount of gasoline that is injected into the engine. So, you had to let older cars warm up before driving or they would stall out. But it's been about 30 years since carbureted engines were common in cars. Carbureted engines were phased out in the late 1980’s and early 1990’s. So, unless you’re still driving your dad’s treasured vintage truck, you need to let go of this outdated practice.

But that doesn’t apply to my vehicle!

While a lot of the mechanics on diesel and gasoline engines differ, this is true for both diesel and gasoline engines. Until your engine has warmed up to its optimal temperature, you should drive your vehicle gently, not let it idle. Fuel injection systems on both engine types also adjust the air/fuel mixture based on engine temperature to compensate for lower temperatures. In the past, gelling of diesel fuel used to be a problem, leading diesel owners especially to adopt this practice in droves. However, fuel refiners have worked to resolve this issue by creating winter blends that better withstand colder temperatures. 

But, but, you’re just plain wrong!

Change is hard, but let’s examine what unnecessary idling does to your engine. Idling causes twice the wear and tear on internal parts compared to driving at regular highway speeds. This increases maintenance costs and shortens the life of the engine. Idling strips lubricating oil away from the engine's cylinders and pistons.

"[That's] because you're actually putting extra fuel into the combustion chamber to make it burn and some of it can get onto the cylinder walls," Stephen Ciatti, a mechanical engineer who specializes in combustion engines at the Argonne National Laboratory, told Business Insider. "[Fuel] is an outstanding solvent and it can actually wash oil off the walls if you run it in those cold idle conditions for an extended period of time." - Popular Mechanics

Even though warm air generated by the radiator will flow into the cabin after a few minutes, idling does surprisingly little to warm the actual engine. Driving your car is the fastest way to warm the engine up to 40 degrees. Once at that temperature, the fuel injection system switches back to a normal air/fuel ratio.

But, but, BUT!

Still don’t believe it? Check your owner's manual to find out the guidelines on idling for your vehicle.

Written by:

Beckie Bean

Digital Content Manager

December 3, 2017

Sources: AutoTrader, Popular Mechanics,

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