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Unless you drive an electric vehicle, chances are you’re driving around town with the help of an internal combustion engine. If your gas-fueled car is sputtering, the spark plugs may be the culprit. When your engine is functioning correctly, spark plugs should last between 20,000 and 30,000 miles.

The U.S. Federal Highway Administration clocks Americans’ average annual mileage at 13,476. Break this down into spark-plug life expectancy, and it comes to between 1.5 and 2.25 years. While spark plugs don’t require frequent attention, they can wreak havoc on your car when ignored.

What are spark plugs?

Spark plugs are like small lightning bolts that create the electricity needed to ignite the fuel/air mixture in an engine’s combustion chamber. They are a critical element in allowing the engine to start and continue running.

Each cylinder of the engine requires one spark plug. Consequently, each spark plug needs a wire that connects it to the coil’s distributor. Spark plugs seem to be straightforward devices, and in theory, they are. However, they also require precise timing to operate effectively.

The bulb-like tip on one end is plugged into the wire head, which creates the high voltage needed to send the energy that ignites the engine. Because the charge can vary from 40,000 to 100,000 volts, a ceramic insulator is required for protection. The electricity created by the alternator travels through the coil, distributor, and the spark plug’s core to the opposite end with the hook-like appearance.

The outer core tab is the electrode. The space between the hook and charged electrode is where the spark is created that ignites the fuel/air mixture in the cylinder.

How do spark plugs work?

The original spark ignites the fuel mixture in the combustion chamber. However, in order to keep your vehicle running, each cylinder requires a series of small explosions. The explosions provide the force to move the pistons up and down.

Each cylinder contains an exact combination of fuel and air. As the piston rises inside the cylinder, the spark plug ignites. The electrical arc creates the pressure to move the piston back down the cylinder and turn the engine. The series continues to repeat as you drive your vehicle.

How often should you replace spark plugs?

Spark plugs could last up to a few years depending on the miles you drive and your engine maintenance habits. The electrode is typically the part that wears out. Your car’s owner’s manual can give you its specifications for optimal performance.

You may stretch the more typical 20,000-to-30,000 spark-plug life expectancy to 40,000 miles if you practice driving at “moderate speeds and with moderate acceleration,” explains Advance Auto Parts. With engineering developments, new car buyers can enjoy an even longer spark-plug life that ranges from 80,000 to 100,000 miles.

One of the critical factors contributing to the health of spark plugs involves how well you maintain the rest of the engine. A valve cover gasket leak, for instance, may cause oil to leak into the cylinder affecting that spark plug’s ability to function properly.

If you’ve noticed the engine misfiring, you should check the spark plugs. Even if they’re relatively new, they can reveal other problems that must be addressed. Keeping up with routine car maintenance is a safety precaution that can save you considerable time, money, and frustration down the road.