What you need to know about Spark Plugs.

What is this?

Spark plugs are little devices inside the cylinder that take in high voltage electricity at one end and create a spark at the other end. There, the spark ignites the gas and air mixture, and the resulting combustion is what ultimately powers the car. This service involves removing the old spark plugs and replacing them with new ones.

Should I do this service when it's recommended?

Yes.

Why do I have to do this?

At the sparking end of the spark plug is a built-in gap between two or more little pieces of metal, called electrodes. When the plug fires, one or more sparks jump that gap and a tiny bit of the metal is burned off. This happens hundreds of times every minute. Over time, the gap between the metal tips gets too big.

Also, your spark plugs can get fouled, but that would indicate that you have a problem.

What happens if I don't do this?

Your engine will start to misfire and run poorly, performance will suffer, efficiency will decrease and emissions will dramatically increase. Your car may also be difficult to start.

Is there any maintenance required between intervals?

We recommend removing the old spark plugs and reinstalling new ones at least every 30,000 miles.

Many manufacturers have long-life, 60,000- or 90,000-mile spark plugs. If you don't remove these spark plugs until they're due to be changed, you might find it extremely difficult or even impossible to remove them when the time comes. You'll also want to examine the plugs if your car is running poorly. A blackened plug, for example, can tell you that the engine is running too rich.

Courtesy of Car Talk