How to Change Auto Spark Plugs

Attaching New Spark Plugs

Before you insert the new spark plug, rub some anti-seize along the threads. Anti-seize will help prevent the spark plug from getting stuck in the cylinder. The next time you need to change your spark plugs they should come out easily. Don't get any anti-seize on the electrodes -- it can cause your spark plugs to fail.

If you can seat the spark plug by hand using the socket wrench extension and spark plug socket, do so. Gently turn the socket counterclockwise to seat it before turning it the other way to screw it into place. It should turn easily -- if you encounter resistance, stop and turn it the other way before trying again. Once the spark plug is snug, attach your extension to your socket wrench or use your torque wrench to tighten the spark plug so that the plug's washer is compressed against the mounting surface. Don't over tighten the spark plug.


Pick up the spark plug's wire boot and replace it. If you have a plastic boot, it should click into place when you plug it in. If your boot is made of rubber, you may want to rub some dielectric grease on the interior of the boot to make it easy to remove in the future. Once you're finished, you can move on to the next spark plug and repeat the procedure. That's all there is to it!

Replacing spark plugs remains one of the few engine maintenance items that the average person can tackle without a lot of knowledge and experience. Just follow our instructions and you should be back on the road with a new set of spark plugs in no time.

Learn more by following the links below.

Related HowStuffWorks Articles


  • "Spark Plug Basics." (Oct. 22, 2009)
  • "The Fuel and Engine Bible." (Oct. 21, 2009)
  • Car Craft. "Choosing the Right Spark Plug for Your Custom Engine." (Oct. 22, 2009)
  • "Dear Tom and Ray." Feb. 10, 1996. (Oct. 23, 2009)
  • Ganesan, V. "Internal Combustion Engines." McGraw-Hill Inc. 1994.
  • How to Change Spark Plugs. "How to change your spark plugs in 10 easy steps." (Oct. 21, 2009)
  • NGK Spark Plugs. "Tech Info - Spark Plugs Overview." (Oct. 22, 2009)
  • "Spark Plug 411." (Oct. 23, 2009)