What is a spark plug? How do they work? Why do they vary in cost?
These are just a few of the questions that we’ll aim to answer for you in this article.
First, before we talk about the different types of spark plugs, you may want to know the function of a spark plug, so let’s go!
What is a Spark Plug?
So, what exactly is a spark plug? A spark plug is used to ignite your fuel as it gets injected into your engine’s combustion chamber. This will only apply to petrol engines as other fuels are ignited by different methods. Your engine will usually have one spark plug per cylinder bore, which gets an electrical feed either directly from a coil pack or indirectly via HT (high tension) leads.
In both cases, a high amount of voltage is generated by your vehicle’s coil pack and then sent through to your spark plugs. This electrical energy that gets transmitted will then jump the gap between your plug’s center electrode and it’s ground electrode. As the electrical charge jumps the gap, it gives off a visible spark (hence the name spark plug), and this is the spark that ignites your fuel causing a miniature explosion which is what keeps your pistons moving and your engine turning.
What makes the spark plug such a great component is it’s simple design. Whilst it remains one of the most vital parts of your engine and does a vast amount of work, they still remain beautifully simple in their method of operation.
Whilst nearly all spark plugs remain the same in how they operate, they do vary in their efficiency, depending on the material they’re made from.
Types of Spark Plugs
The most common types of spark plug types are the copper spark plug, iridium spark plug, platinum spark plug, and double-platinum spark plug.
We’ve crafted a handy list for you which includes the difference in materials used and the differences in efficiency and cost.
1. Copper Spark Plugs
Copper spark plugs are the common name for most basic spark plugs that you can get hold of. However, this term is quite incorrect, as standard material plugs do not have electrodes made from copper because copper is a very soft material that will melt fast.
A “Copper Spark plug” or standard spark plug uses a nickel-alloy that may include a small copper core. Actually, all types of spark plugs include a copper core inside of them.
The body of these copper spark plugs is physically the largest out of all the ones listed here. This is due to how inefficient they are compared to a larger voltage to generate a spark.
These plugs are best suited to older vehicles that don’t have lots of accessories fitted to them and have a basic performing engine.
Plugs such as these tend to be fairly cheap to purchase and usually won’t cause any problems as long as they’re changed at regular service intervals – depending on what the manufacturer recommends.
2. Iridium Spark Plugs
These are some of the top tier plugs that you can get your hands on in the standard consumer market. Being made from Iridium, they will last much longer than standard copper plugs and platinum plugs.
This is mainly because of how durable iridium is as a metal. Not only is it incredibly strong and durable, but it’s also a great conductor. This means that the plug’s body can be a lot smaller as it doesn’t require as much electricity to generate a spark, which makes them much more efficient also.
You probably think that iridium sounds pretty awesome – and it is, which is why it comes with a heavy price tag.
Although these plugs are quite expensive, however, they’ll usually last around 50,000 miles which means they don’t require changing very often at all.
Iridium plugs are often fitted to newer vehicles running higher performance engines; if this is the case for you, we recommend replacing your spark plugs like for like.
3. Platinum Spark Plugs
Platinum spark plugs are fairly similar to copper spark plugs in their makeup, except they feature a platinum tip design that is welded to the end of the center electrode, making it much more durable and longer-lasting than the basic nickel alloy tip featured on a copper spark plug.
Platinum spark plugs can usually last around 100,000 miles due to their better durability and improved ability to handle higher temperatures.
Whilst these plugs are neither the most efficient nor the most durable plugs on the market when compared with iridium spark plugs, they do come at a lower cost. This is what makes them a great middle ground for your vehicle, provided your manufacturer specifies them.
4. Double Platinum Spark Plugs
Again, these double platinum spark plugs are similar in design to both a copper and a single platinum spark plug, except they feature a laser welded platinum inlay.
This double-platinum design on both the electrode and the inlay makes these plugs even more efficient and durable—all for a lower price than Iridium plugs.
These are a great option if you would like an upgrade from single platinum spark plugs, but don’t want to pay out for iridium plugs.
RELATED: 6 Causes of Oil on Spark Plugs
Hopefully this guide has given you an insight into the main differences between the 4 most common spark plugs on the market. As with most things, it’s good to balance spending money up front with potential repairs that need carrying out in the future.
Spark plugs are a vital component in your engine and wont run without them. They’ll not only keep your engine running efficiently but also smoothly. This is why it’s so important to spend the time and money on proper maintenance.
Do you want to know which is the best spark plugs to choose? Check out our other guide: best spark plugs.
Please feel free to refer back to this guide whenever you need to for a help hand.
Share this Post
Founder, owner & main author of Mechanic Base. I have been repairing cars for more than 10 years, specialized in advanced diagnostics & troubleshooting. I have also been a drifting driver and mechanic for over 7 years.