Spark plugs don't last forever. Like most other parts of your vehicle, your spark plugs can only go for so long before they require replacement. When it comes to replacing spark plugs, however, the common question is usually "when?"

How often you should have your spark plugs replaced depends on a lot of variables, including your vehicle manufacturer's own recommendations and your vehicle's current performance and condition. Let's dive in deeper for some more concrete answers.

Wait…What Does a Spark Plug Do?
Engines need three things to breathe life into the combustion process - air, fuel and spark. Spark plugs provide the latter by essentially shooting a high-voltage spark into the cylinder just as air and fuel enters the combustion chamber. This spark ignites the air and fuel mixture, providing the explosive force needed to push the cylinder down and complete the combustion process.

Most cars have at least as many spark plugs as cylinders, although many vehicles have a "dual spark" set up that doubles the number of spark plugs used per cylinder for more precise ignition and better performance. Some spark plugs use a copper electrode, although most modern spark plugs use iridium or platinum for a more reliable and precise spark. 

Why Do My Spark Plugs Keep Going Bad?
Unless you actually remove and carefully inspect your spark plugs, it's hard to tell if and when they suddenly go bad. However, there are a few symptoms that could give you a heads-up to trouble on the horizon. If your care exhibits any of the following, then you may want to have a professional check your spark plugs:


Mansfield Motor Group

1493 Park Ave W
Directions Mansfield, OH 44906

  • Sales: (419) 869-3260
  • Service: (419) 871-5977


  • Monday 9:00AM - 7:00PM
  • Tuesday 9:00AM - 6:00PM
  • Wednesday 9:00AM - 6:00PM
  • Thursday 9:00AM - 7:00PM
  • Friday 9:00AM - 6:00PM
  • Saturday 9:00AM - 5:00PM
  • Sunday Closed
  • Car struggles to start or fails to start at all
  • Poor, uneven idle
  • Loud knocking or pinging, especially on acceleration
  • Sluggish acceleration and poor overall performance
  • Fuel economy that's worse than usual
  • "Check Engine Light" appears on the dashboard
  • Smoky, sooty and/or heavy exhaust

As for what actually causes your spark plugs to go bad, here are a few possibilities to consider:

  • Heavy oil and fuel deposits can foul the spark plugs, preventing the spark from firing off properly.
  • Spark plugs that aren't gapped properly can reduce engine performance and even cause knocking and pinging.
  • A completely dead spark plug can cause the engine to misfire, which reduces performance while causing potential damage elsewhere.
  • Actual physical contact between the cylinder and spark plug can cause the spark plug to break off, potentially causing catastrophic damage to the cylinder, cylinder walls and valves.

Taking good care of your engine is the key to long-lived spark plugs. For instance, regular oil changes help prevent spark plugs from becoming fouled with unwanted deposits. Most spark plugs also come pre-gapped for ease of installation, but it's always a good idea to double-check the gap prior to installation.

Why Change Your Spark Plugs at All?
You're probably wondering "why should I even bother changing my spark plugs at all?" As mentioned before, spark plugs play a crucial role in your engine's operation. Leaving the same set of spark plugs in your engine well beyond their recommended replacement interval could potentially damage your engine, let alone have consequences for your vehicle's overall performance.

Not only does your vehicle start and drive more smoothly with fresh spark plugs, but you'll also improve your vehicle's emissions. If you live in an area with active vehicle emissions testing, then you know how important it is to keep every part of your vehicle in top shape.

Common Spark Plug Replacement Intervals
So, how often should you change your spark plugs? That depends on a variety of factors, including the type of spark plugs your vehicle uses:

  • Ordinary copper and nickel spark plugs should be changed every 30,000 to 50,000 miles, unless otherwise suggested by the spark plug manufacturer.
  • Platinum and iridium spark plugs tend to last longer than standard copper and nickel spark plugs. Expect to change them every 60,000 to 150,000 miles unless otherwise noted.

Other factors that could affect your vehicle's spark plug replacement interval include how you use your vehicle. If you subject your vehicle to high performance driving on a regular basis, for example, you may need to change your spark plugs more often. Constant idling, frequent towing and driving in severe heat or cold weather conditions may increase how often you'll need to replace your spark plugs.

The easiest way to find out how often you'll have to replace your spark plugs is simply by following your vehicle owner's manual. It'll have all of the information you'll need to ensure your vehicle receives timely care.