QOTD #61: Does idling hurt your car’s engine?

During my time as a driver manager with a fleet of 40 vehicles, I have noticed that some of our vans have developed catalytic converter problems. The most recent was a 2012 Dodge Grand Caravan (with 123k miles) which developed a check engine light with a P0420 code. The local mechanic told me it was the bank one catalytic converter needing to be replaced. This expensive repair caused me to wonder why the unit went bad.

The company I work for transports railroad crew members from one place to another. However, there are times when the crew is not ready to go for up to three hours. As you can imagine, if it is hot, the driver will keep the van running with the AC on. Now that colder weather has arrived, our drivers keep the van running for the heat. While I don’t have a problem with our drivers being comfortable, I am wondering if the idling of their vehicles is causing problems to develop inside the engine or catalytic converter.

Search the internet and you will find forums arguing about this:

“Not true. 90% of all wear is done at start up. Once an engine is running it’s best to leave it running. Letting it idle will not harm a thing. Not back then and not today. As long as the engine has oil pressure you’re not hurting a thing. Sorry but dad was wrong.” 1

“The main problem with extended idling was the wasted fuel, fouled spark plugs, and carboned up combustion chambers from the carburetor delivered fuel system and lesser ignitions systems of the era. … But, the company my mom worked for at the time in the mid-1960’s used a fleet of Corvairs, including the van version, and without any particular problems for all of the extended idling that the delivery units were subjected to.” 2

So… who is right? And how about with newer, fuel-injected engines today? Does idling cause your vehicle’s engine to foul spark plugs, wear out quicker, and mess up your catalytic converter? Instead of relying on the forums, I decided to visit the Car Talk website to find the answer:

These days, with fuel injection and computer engine management, cars and trucks can idle until they run out of gas without doing any extra damage to the engine (assuming the cooling system is working properly). Idling does add wear and tear to the engine –anytime the engine is running, you’re decreasing the useful life of the oil and slowly wearing out parts. But it’s no more harmful than driving. 3

What do you think? Is Car Talk right about this?

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