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Understanding Spark Plugs – Various Types and How to Select the Best

Whenever the car does not work you are obviously going to be worried as there could be a large bill on the way. Stalling can be a big problem, but it can also be something that you will be able to fix. Very often the issue will be with the spark plugs and this can be an easy change to make. Plugs must be in great working condition, or the car will not be going anywhere. They are needed to get the engine started and if they start to fail, so will the engine. Now you understand how important they are you need to know what kinds are out there.

Type of Spark Plug

There are 4 main types: –

  • Iridium
  • Platinum
  • Double Platinum
  • Copper Core


These are considered by many people to be the best ones to use if you are looking for high performance. They last up to 25% longer than the next best ones, and as you can imagine, for this reason, they are the most expensive type. They have an electrode of 4mm and this is the smallest of all types.


You will still get a great deal of mileage from these plugs as it is estimated that they will last for 100,000 miles. These are the plugs that will be fitted into many of the new cars that use a distributor-based system.

Double Platinum

These will provide a higher performance than the other platinum plugs, but unfortunately not twice as good. It is classed as a waste spark and this means that the compression receives a spark and then the spark is wasted when it returns. They are more expensive again, but unless the car should have these, it will not be worth the added expense.

Copper Core

If your car dates to the 1980’s, then these are the sort of plugs you will need. They are ideal for a car with a carburetor. They are the plus with the largest diameter electrode as it is 2.5 mm.

Why Use Spark Plugs?

Electricity is needed to reach the combustion chamber. It may only be a small distance, but this needs to happen. Once inside the chamber they ignite the oil that is stored there. It is only when this has happened that the engine will run, so problems will arise if they are not in good working order. They also help to take the heat out of the combustion chamber and taking it to the cooling system. It is for this reason that they should be high quality or they will not be able to stand the heat.

What to Look For

  • Size – The plugs should be the right size for the cylinder head
  • Quality – The materials used during construction will decide the quality of the plug. A poor quality one will not last very long.
  • Function – They will take away the residue formed by the combustion process meaning less cleaning is needed. It is possible to change them at home, but they can also be changed during a general service.

Changing the Plugs

Different types will last for different periods of time. An iridium one can run for 125,000 miles and a platinum one, 100,000 miles. A high-performance engine will reduce this amount as there will be a lot of war placed on them.

Reasons You May Have to Change the Spark Plugs

  • Jittery sound when idle. Vibration is a bad sign.
  • Slow to start – Worn plugs won’t work
  • Engine misfiring – Emissions will also increase
  • Surging – Sharp and jerky movements is a sign of poorly performing plugs.
  • Lack of fuel efficiency
  • Limited acceleration

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