spark plug types

Copper vs Iridium vs Platinum Spark Plugs – Differences & Information

In General by Magnus Sellén4 Comments

Spark plugs are essential components for generating the spark required to ignite the air-fuel mixture in the combustion chamber.

This is done by means of an electric current that is conducted to the plugs. The heart of the spark plugs is the side and center electrodes.

At one point in time, the electrodes were made of copper, which was later converted into platinum or iridium. This has led to manufacturers making plugs from all three of these materials. Choosing one of these materials can be confusing if you are not an expert.

When searching for the right spark plug, you must take into account its conductivity. Plugs need an electric current to produce a spark for ignition. One of the best conductors for electricity is copper.

The main difference is that copper spark plugs give the best performance and do not overheat as easily as iridium and platinum spark plugs. Platinum spark plugs have a long service life, but low power. Iridium spark plugs are the most expensive and have a long lifetime and a pretty good performance.

Copper spark plugs

spark plug

When it comes to electrical conductivity, nothing beats copper. That’s what made copper spark plugs one of the best. In copper spark plugs, a nickel alloy is used for the center electrode. The disadvantage of the nickel alloy is that it is soft, which makes it not very durable.

In addition, it needs a lot of voltage so that the current can flow. Older cars still use copper spark plugs because their electrical requirements are not very high.

The reason why most manufacturers use metal on the sides and in the middle of the electrode is the low melting point of copper. Electrical current is passed through the spark plug body and a spark is created between the gap between the middle and side electrodes. If you are unsure, refer to your service manual to find the correct spark plug specifications for your engine.

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The spark is vital to the combustion of air and fuel. The use of metals such as platinum and iridium delays the spark and reduces the risk of misfiring.

Advantages of copper plugs

  • Plus are readily available and cheap.
  • Plugs have a fast cooling rate that boosts performance.
  • Mostly used in older cars.


  • Wear out fast at less than 20,000 miles.

Iridium spark plugs

If you are looking for spark plugs that last longer, iridium plugs are the best choice. Iridium is harder and more durable than copper or platinum, but more expensive. In addition, the plugs are perfect for a power-hungry car because the center electrodes are small.

This means that it needs less current to produce a spark. The trend is slowly moving towards greater use of iridium spark plugs.


  • The highest melting point of the three plugs.
  • Last longer than platinum and copper.


  • Most expensive.

Platinum spark plugs

The platinum plugs last longer than the copper plugs, but not as long as the iridium plugs. A platinum disc is melted on the tip, which makes the plugs resistant to deposits. The plugs are suitable for car owners with electronic distribution systems.

In addition to the normal platinum spark plugs we also have the double platinum spark plugs. This eliminates the probability of a wasted spark.

In such cases, your platinum spark plugs will ignite twice: once in the exhaust stroke cylinder and again in the compression stroke cylinder. This spark in the exhaust stroke cylinder is often wasted.


  • Long-lasting: can be used for up to 100,000 miles.
  • They do not overheat easily.

What will happen if you do not replace the spark plugs?

copper spark plug

Spark plugs are indispensable for generating the necessary ignition spark to ignite the fuel and air mixture. However, depending on the type of your plugs – platinum, copper or iridium – you may be forced to change them earlier.

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During routine maintenance, you should change the oil filters, engine oil, fuel filters, but you should also check the condition of your spark plugs. The plugs should be changed at intervals of between 30,000 and 50,000 miles. Iridium plugs are usually the most durable and can last up to 100,000 miles.

But when will you know that your plugs have outlived their useful purpose? You can learn more in-depth symptoms of bad spark plugs here.

Slow acceleration

A worn plug will not send the required charge to the combustion chambers. This means that one of the car’s combustion chambers is not working as usual. Most modern engines have on-board computers that regulate the current to the spark plugs. In this case, the slow acceleration could be due to a defective sensor. Clogged fuel injectors or dirty air filters can also cause slow acceleration. Your mechanic can identify the exact cause of the problem.

Engine misfiring

When you start having problems with engine misfiring, the culprit is often defective spark plugs. To ignite the fuel-air mixture, the combustion chambers need a charge provided by the spark plugs. The wires connected to the spark plugs could also be damaged, causing the incorrect current to flow.

If your engine misfires, you will hear stuttering or tripping noises from the engine block. This leads to an increase in exhaust fumes and reduced mileage.

High fuel consumption

Since the fuel in the combustion chambers does not ignite completely, you will notice a decrease in gas mileage. If the spark plugs are defective, the gap between the side and center electrode is often too large or too small. This means that no charge is generated for combustion.

In this case, you do not necessarily have to buy new plugs. You can remove existing plugs and either widen or narrow the gap between the electrodes according to the manufacturer’s settings.

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Problems starting the car

A well functioning engine should come to life the moment you turn on the ignition key. If your plugs are worn out, you will find that you need to turn on the ignition several times before the engine starts. You may also have problems with your alternator.

Spark plugs are not designed to last forever and should be checked occasionally for wear.


Spark plugs are necessary for effective combustion of the air-fuel mixture. For a very long time, only copper spark plugs were available. While copper is a good conductor of heat, the plugs wear quickly and must be replaced every 20,000 miles.

Platinum spark plugs have a long service life and eliminate the probability of a waste charge. Iridium spark plugs are the best plugs because of their durability but are more expensive than platinum and copper spark plugs.

4 thoughts on “ Copper vs Iridium vs Platinum Spark Plugs – Differences & Information ”

  1. Thank you Magnus, I would like your recommendation on spark plugs for a 2001 BMW 740il.
    Thanks much.

  2. This may sound stupid, but can I use a paperclip & jumper wire to check my OBD1? (92 mercedes 400se-38 pin)

    1. No problem, it will work. I’ve often used a paperclip for a jumper. Better connection if you have the recommended connector of course, but sometimes got to use what ya got, eh?

  3. In ancient times we used steel tipped spark plugs, a fact you do not mention (at least we always called them such). We are talking Champion and Delco and Autolite, all-American plugs that lasted maybe 6000 miles before performance drop off, very common in the days of the 6k tune up interval for ANY stone ax era points-fired car. They were so-so, though when the Champion extended tip “Y” series appeared, as in J12Y for my old 60’s Pontiac, they seemed to make a real difference, putting the spark closer to the center of the chamber a few MM and I noted better gas mileage… 5-10% on my delivery routes. Almost all plugs these days are extended tip and exceed our “stone knives and bear skins”.

    Then I got my 1970’s UJM (Universal Japanese Motorcycle) and found a more modern type that worked really well, like the Nippon Denso U-groves. The U-grove plugs are still the best for my ancient 1978 Yamaha XS-650SE motorcycle (which I discovered a ways back are a copper core design). Nothing comes close for solid performance and cold start ease and I didn’t mind swapping them every 10-12k. That was what you did then (and 10k was a lot more than 6k after all). From that experience I switched and have enjoyed using them in all my old machines, even lawn mowers, for decades.

    My modern cars have all OEM specced for Platinum and Iridium’s. The Iridium’s are definitely better of the two, but vs old-school copper… don’t know. Never tried them in new cars. Above I discover they might be a better choice for us old wrenchers who care about every mile being “righteous” and love to get our hands dirty blacksmithing our rides. Thank you for that Magnus. My modern rides will give them a trial vs their OEM spec. Maybe get back to you if I can remember to. ;^D

  4. Due to very high demand and a high amount of comments, you might have trouble getting your comment answered by me. If you want to get fast answers from a certified automotive technician you should ask your questions here: Ask A Mechanic

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