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What Is a Spark Plug? How to Know If It Needs Changing

Educational  ·  August 31, 2020

What Is a Spark Plug? How to Know If It Needs Changing

While EVs slowly take over the car world, many people still drive regular ICE vehicles. Internal combustion engines work by compressing air and fuel before that mixture explodes (or 'combusts') and generates power. These explosions happen thousands of times every minute the car is on.

Have you ever wondered what triggers those explosions? Air and fuel don't combust by themselves, so something needs to give it that initial spark - and that's where the spark plug comes in.

What Does a Spark Plug Do?

Attached to each of your engine's cylinders is a spark plug. It quietly does a very straightforward job: It creates a spark that ignites the pressurised mixture of air and fuel to power your car.

In this article, we'll look at what spark plugs are made of, how they work, and most importantly, how to tell if they need to be changed.

What Are the Parts of a Spark Plug?

Spark plugs might come in different sizes, but they're generally built the same. Bear in mind that the top half will stick out of the engine cylinder, while the other half will be inside the cylinder.

At the top half, you have the terminal which is connected to the car's electrical system. Inside, there's a ceramic resistor and a core usually made of copper. 

All these parts are then housed in a metal shell with a gasket to attach it snuggly to the engine cylinder. That gasket helps you avoid getting oil on the spark plug.

Here's the essential part of the spark plug: the electrode at the bottom of the plug. The electrode is located inside the engine cylinder.

As far as spark plug function is concerned, power flows from the terminal down to the electrode where sparks are generated. Just like I mentioned earlier, this process happens thousands of times a minute whenever the engine is on.

Are There Different Kinds of Spark Plugs?

When you shop for spark plugs, you'll notice that there are copper, platinum, and iridium spark plugs. What's the difference?

The difference is in the metal used in the spark plug. All three kinds of metals will conduct electricity differently and have different lifespans.

Copper spark plugs perform best in conducting electricity efficiently. They conduct heat equally well.

You may have heard about the supposed superiority of platinum spark plugs. That’s not always true because platinum is not as good a conductor as copper. As a result, it also has a higher chance of overheating. 

Iridium spark plugs, like NGK spark plugs, are a little different. They perform better than platinum, and they last longer than copper plugs. That's why iridium spark plugs tend to be more expensive.

When Do You Change a Spark Plug?

Remember: spark plugs generate sparks thousands of times per minute. That's a lot of wear and tear! Eventually, you'll need to change those spark plugs for new ones. 

Here are three signs that your spark plugs need changing.

  1. Your engine idles roughly or misfires – when your spark plugs are worn-out, they cause your cylinders not to fire correctly. As a result, you'll notice your engine idling roughly or even misfiring while you drive.
  2. Your fuel consumption is higher than usual – bad spark plugs will result in inefficient combustion where the air/fuel mixture doesn't burn correctly. As a result, you'll notice your fuel tank emptying sooner than it usually does.
  3. Starting your car and accelerating is difficult - starting your car in the morning is difficult enough for a cold engine, but with lousy spark plugs, it’s even tougher. The same engine will also fail to produce the power you need when accelerating.

What Happens If You Don't Replace Bad Spark Plugs?

Faulty spark plugs should be replaced as soon as possible. Sadly, some people procrastinate or ignore the problem entirely. So, what happens if you don't fix the problem immediately?

Bad spark plugs will only get faultier with time. As that happens, your engine will gradually lose even more of its performance. Like mentioned above, your fuel efficiency will drop, and simple things like starting or accelerating your engine will be difficult to do.

As a worst-case scenario, your engine might stop working entirely. If you can't start your car at all, you'll end up spending much more money. You'll need to pay to get your vehicle towed, or you'll have to replace the spark plugs on the spot.

All of that can be prevented by addressing spark plug problems right away. Replace them as soon as they become problematic. 

If you can afford it, you should take a more preventative approach. You can start by replacing all spark plugs during scheduled maintenance, regardless of their condition. That way, you'll never have to worry about your spark plugs at any other time!

Finding Solutions Early

Spark plugs are the kind of service part that you can get from almost anywhere. You can even get them online! No matter where you get them from, it's essential to make sure that you understand what they are and how they work.

Whether it's about spark plug problems or anything else related to your car, you can head over to to find a solution!

By Ray Hasbollah

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