What Causes Spark Plugs to Wear Out?

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Without operational spark plugs, your engine won’t run. If even just one plug were to fail, the change in functionality would be very noticeable. Your engine would run rough, it would idle poorly, it might spit and sputter during acceleration, and it might even stall out on you. Spark plugs do wear out over time, although the actual lifespan varies depending on the type of plug in question, the condition of your engine, and your driving habits.

Wear factors for spark plugs

There are several factors that play a role in spark plug health, but the most common reason for them to wear out is that they’re just old. To understand this, you need to know a bit more about how spark plugs work.

When your alternator generates electricity, it is sent through the ignition system, down the spark plug wires, and to each individual spark plug. The plugs then create electrical arcs at the electrodes (the small metal cylinders protruding from the bottoms of the plugs). Each time a plug fires, a minute amount of metal is removed from the electrode. This shortens the electrode, and requires more and more electricity to create the arc necessary to fire the cylinder. Eventually, the electrode will be so worn that it won’t arc at all.

This is what happens in a normal, properly maintained engine. There are other factors that can reduce plug life (all spark plugs eventually wear out; it’s just a question of when).

  • Overheating Damage: Overheating spark plugs can cause the electrode to wear faster. Pre-ignition from an improperly timed engine can cause this, as can an incorrect air to fuel ratio.

  • Oil Contamination: If oil seeps onto the spark plug, it will foul the tip. This creates damage and additional wear (oil seeping into the combustion chamber is something that happens over time as seals begin to fail).

  • Carbon: Carbon buildup on the tip can also cause premature failure. This can happen due to dirty injectors, a clogged air filter and many other reasons.

As you can see, there are a number of different factors that affect when your spark plugs will fail, and just how much use you’ll get out of them.


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Fred

16 years of experience
350 reviews
Fred
16 years of experience
Honda Odyssey - Spark Plugs - Humble, Texas
Fred arrived on time and got to work immediately. He wouldn’t even take me up on my offer of coffee.....or lunch. He was very competent and efficient., and personable. We talked about a common interest, Air Force jets (I made sure not to distract him). Fred completed the work in less time than expected to my complete satisfaction. I will talk Fred and Yourmechanic up to friends and family and will definitely use Yourmechanic again.
Chevrolet Equinox - Spark Plugs - Spring, Texas
Fred was timely and finished the work within the timeframe quoted. He was personable and I would like to use him for future services.

Juan

8 years of experience
33 reviews
Juan
8 years of experience
Kia Rondo - Spark Plugs - Chapel Hill, North Carolina
Juan Esteban did an excellent job. He was knowledgeable and gave me honest feedback on what was urgently needed and what could be a bit delayed. I trusted his judgment and my car works great. Looking forward to using You Mechanic again and especially waiting for Juan to return from his holiday leave to book my next appointment.
Porsche Boxster - Spark Plugs - Cary, North Carolina
My first time using Your Mechanic. Juan was great. He really knows and cares about the cars he works on. Juan Worked on my Porsche in the cold and rain under a tarp he made from a hanging branch on a tree. He is very knowledgeable and explained everything in detail about what he was doing. Would highly recommend Juan.

Robert

12 years of experience
6 reviews
Robert
12 years of experience
Ford Fusion - Spark Plugs - Stockton, California
Robert was very knowledgeable and professional. He is also very friendly and likable individual. I’m very pleased and satisfied with his work.

Gregory

30 years of experience
245 reviews
Gregory
30 years of experience
Toyota Echo - Spark Plugs - Littleton, Colorado
Very personable and obviously cares about his work. Greg is knowledgeable about his work and takes the time to answer all questions. I will definitely call again and request Greg.

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