How Often Should I Have My Spark Plugs Replaced?

• Spark plugs generate the electrical arc that ignites the air-fuel mixture, and they are a scheduled wear item, not a lifetime part.
• The common warning signs are rough idle, sluggish acceleration, hard starting, a Check Engine light, and falling fuel economy.
• Replacement intervals typically fall between 30,000 and 90,000 miles.

Spark plugs create a quick electrical arc that ignites the mixture of fuel and air inside the combustion chamber of your engine. This burst of energy forces the pistons to move. The crankshaft transforms that movement into rotating the wheels, which propels your vehicle forward.

Diesel engines do not contain spark plugs because they rely on greater compression ratios to create combustion.

The primary reason that spark plugs wear down is because of time. The anti-corrosion coating that protects this component eventually wears out. Oil, carbon, and other dirt can now reach the plug and build up on it.

A bad fuel filter is another reason because this enables dirt, grime, and other contaminants to enter the fuel system. The grime eventually accumulates on your spark plugs and erodes the insulators, forcing electrical sparks throughout the engine instead of in the proper location. Misfiring and ineffective timing then affect your engine performance.

When your spark plugs begin to wear out, it affects how your engine performs. The following are some of the signs.

Rough idling. You hear strange noises such as knocking or rattling coming from your engine as you drive as well as feel unusual vibrations because your engine misfires.

Slow acceleration. When your spark plug is too dirty to function optimally, it does not create the spark effectively, making your car feel sluggish. Your engine might stop, stall, and then sputter before it starts again. This can prove particularly dangerous if you're on a highway where traffic is traveling at top speed.

Hard starting. You might ordinarily think that the reason your vehicle has trouble starting is because of a faulty battery. This is particularly true if none of the electrical parts inside the cabin are working. However, if your spark plugs do not produce enough spark due to being worn out, your engine may also be difficult to start.

Check Engine light is on. This light on your dashboard comes on for many reasons, including a loose fuel tank cover, a faulty oxygen sensor, or a serious engine problem. It also illuminates when your spark plugs are starting to fail. A steady light may mean a misfire, which can be addressed later. A blinking light may indicate a more serious problem that demands that you change the spark plugs immediately.

Poor fuel economy. If you notice that you’re getting few miles to the gallon, faulty spark plugs may be forcing the engine to work hard, which leads to more gas being used up and more emissions being produced.

If none of the previous issues are forcing you to replace your spark plugs, you can typically change them every 30,000 to 90,000 miles depending on the make and model of your car.