What kinds of spark plugs are there?

What kinds of spark plugs are there?

There are many types of spark plugs, and their mechanic and electric characteristic vary a lot. All spark plugs are characterized by a specific code and its meaning is decided by their manufacturer.

This is a general review of their main characteristics so that you can identify them:

  • Diameter of the thread: 10 mm, 12 mm, or 14 mm
  • Length of the thread: 0.460 inches, 12.7 mm, 0.708 inches, 19 mm, and 25 mm
  • Hexagon size: it depends on the thread size. 5/8 inches, 18 mm, and 13/16 inches
  • Seat: conical or flat
  • Insulator length: the length between the thread and the end of the spark plug.
  • Resistor spark plugs: they prevent any interferences between the electric system and the car.
  • Electrode material: made of copper (the conventional type), Iridium, or Platinum. The last ones last longer and their spark is better.
  • The number of electrodes: you can find spark plugs with 1, 2, 3, or 4 electrodes. When there are more electrodes, they deteriorate less.
  • Heat rating: this value indicates how much heat the spark plug dissipates. If it does not dissipate a lot of heat, the fuel may self-ignite itself, and this will affect both the performance and the autonomy of the car. This number can be found in spark plugs under their brandmark
  • Calibration: distance “d” between the central electrode and the earth electrode. If the separation is too small, the spark will also be small, and it will be hard to start the car. If it is too big, the spark may not be produced. You should always follow the calibration stated by the manufacturer.
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