Who ever knew something so tiny could have such an important job? 

Maybe you’ve heard about them. Maybe you’ve seen them, or even held one in your hand. But understanding the importance of a spark plug will help you better define your maintenance schedule. 

Spark plug replacements aren’t something you’ll do as often as changing the motor oil, but forgetting about them can lead to a lot of problems with your car. 

Spark plugs have an important job

Without spark plugs, your car wouldn’t go. They play a crucial role in the ignition process. 

When you turn the key (or press the button), the spark plug ignites the air-fuel mixture inside the engine’s combustion chamber. This tiny little “boom” generates the necessary power to drive away and move on with your day. 

Spark plugs convert electrical energy from the ignition system into a spark, which in turn ignites the air-fuel mixture. It’s a precise process that happens in a split second – you’ll know if anything is off. Worn or faulty spark plugs can lead to misfits, reduced fuel efficiency, and engine performance issues. 

What is a spark plug

Have you ever looked at a spark plug? It’s a small resource that packs a big punch in the overall ignition process. 

Take a closer look. The outer metal casing is threaded so it can be installed into the engine’s cylinder head. Inside this shell is an insulator made of ceramic material. This prevents electric current from leaking out. It ensures the current travels to the electrode. 

Tip the spark plug, and you’ll see an electrode protruding from the combustion chamber. This is how the spark plug receives the electric current from the ignition system. On the opposite side is a ground electrode. The gap between is where the spark occurs to ignite the air-fuel mixture.  

When the ignition system sends a high-voltage electrical pulse, the spark plug ionizes the air-fuel mixture in that gap between the electrodes, creating a spark. This initiates the combustion process, and voila – the engine receives power. 

Spark plug replacement – what your car needs

Every time you go to the store, you have choices. Dozens of toothpaste options. A wide variety of cleaners for your home. 

While spark plugs might not have dozens of options, there are different types depending on how your vehicle was manufactured. 

First off, you’ll find three different types of spark plugs available:

Copper spark plugs are the least expensive and have the shortest lifespan. They typically last 20,000 to 30,000 miles. 

Platinum spark plugs offer more durability, and should last between 60,000 to 100,000 miles. They are more expensive but will provide better performance. 

At the top of the list are iridium spark plugs. They are known for exceptional durability and longevity, lasting up to 120,000 miles or more under normal driving conditions. They are the most expensive, but their longevity might offset their higher initial cost. 

You can’t trade between them. Check your vehicle’s owner’s manual to determine what’s best for your car. Then, stick with them for optimal performance. 

But keep in mind that you impact how many miles they’ll last. 

Stop-and-go city driving, towing heavy loads, or frequent idling all wear down spark plugs. If your engine burns oil or runs rich or lean, it may impact a spark plug’s lifespan. Regular maintenance matters, too. Without periodic inspection and cleaning, they might not last as long. 

How spark plugs fail

Regular maintenance ensures lifespan, but even in the best of circumstances, a spark plug will eventually fail. Parts can only last so long. 

What causes failure:

During regular engine operation, carbon deposits can accumulate on the electrodes of the spark plug. These deposits can insulate the electrodes, preventing the spark from jumping across the gap and causing misfires.

If oil leaks into the combustion chamber, it can coat the spark plug electrodes, reducing their ability to conduct electricity and generate a spark. This can happen due to worn piston rings, valve seals, or gaskets.

Incomplete combustion can lead to the buildup of carbon deposits on the spark plug electrodes, causing them to become coated and unable to produce a spark effectively.

Excessive heat can damage the insulator or electrode materials of the spark plug, causing them to degrade or melt. This can occur due to a lean air-fuel mixture, advanced ignition timing, or operating the engine under heavy load for extended periods.

As you can imagine, igniting that air-fuel mixture doesn’t always go according to plan. Sometimes it ignites prematurely in the combustion chamber, before the spark plug fires. This can cause the electrodes to overheat and melt, leading to spark plug failure.

And, of course, physical damage can occur at any time. Maybe they’re installed incorrectly, or the engine vibrates enough to cause damage. In any case, they get to a point where they no longer work as designed. 

3 – 2 – 1 – ignition excellence

What we all want is for our cars to last longer, without headaches, and be a reliable means of transportation whenever we want it. Every part of your car has things you can do to keep it in optimal condition. For a spark plug, this amounts to several things. 

Start by choosing the right spark plugs. We mentioned earlier that your vehicle’s manufacturer recommends spark plugs based on your specific engine. Sticking to this plan ensures you give the engine what it wants and needs for better ignition performance. 

Like other parts, regular inspections work well. You can do it, or you can rely on a mechanic you can trust to do the job well. The inspection should include looking for any signs of wear or damage. 

Every spark plug has a suggested timeline for replacement. At a minimum, you should follow this schedule and replace them for optimal performance, even if they still appear to be in good condition. It’s a way to ensure they won’t degrade rapidly and cause problems when you least expect it. 

This is a job you should leave to the professionals. Manufacturers recommend torque specifications – that means you should avoid overtightening or damaging the spark plugs as you install them. Pros have the proper tools and understand how to install them without stripping the threads. 

Even though you won’t replace them for tens of thousands of miles, don’t forget about them. A trusted mechanic will include inspecting them as a part of regular maintenance. When they check the ignition system, they’ll look at spark plugs, distributor cap, and make ignition timing adjustments, as necessary. 

It might not sound like something you should remember, but bringing your car in for inspections is something to do regularly. It’s just a safety check to ensure your car is running well. 

And isn’t that ultimately what you really want?