What Causes Spark Plugs to Wear Out?

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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Greg

22 years of experience
86 reviews
Greg
22 years of experience
Ford Escape - Spark Plugs - Chandler, Arizona
In my past, mechanics have gotten a bad rap for overcharging and underdelivering. It is good to know that good, hard-working, professional people still exist. It matters and it's appreciated. Greg Fowler gives mechanics their good reputation back. Greg showed up to fix my car two days in a row, resolved the problem of my car not starting, like a jigsaw puzzle master. There was no challenge that he did not tackle head-on. In the end, Sugar (my car) is running sweet again.
Mazda CX-9 - Spark Plugs - Apache Junction, Arizona
Greg was very professional and was not in a rush. He was very knowledgeable and informed me about what was being done. When I was asking questions he gladly answered them. I will be booking him for future appointments.

Joseph

20 years of experience
556 reviews
Joseph
20 years of experience
Chevrolet Trailblazer - Spark Plugs - Salt Lake City, Utah
Joseph is the ONLY mechanic we trust to work on our vehicles. He is thorough, friendly, knowledgeable, and happy to explain things to the minute detail if needed so I understand what he is doing and why. ABSOLUTELY recommend Joseph!!!

Caz

17 years of experience
77 reviews
Caz
17 years of experience
Toyota 4Runner - Spark Plugs - Mableton, Georgia
Caz did a great job. True professional and installed confidence my 4Runner was in good hands. Service was super convenient and price was better than the dealer or local brick and mortar shop. Highly recommend

Jason

32 years of experience
360 reviews
Jason
32 years of experience
Lincoln MKZ - Spark Plug Replacement - Phoenix, Arizona
Jason is one of those few mechanics that come once in a lifetime. Very knowledge in all makes, especially mine! Look forward to working with Jason again. I learned so much!

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