On the white part of spark plugs there are those colored rings. In amount ranging from 0 to 4.

What does the amount of rings refer to? And what does it's color refer to? Is it just aesthetics?

Different spark plugs

  • I wonder if it like resistors except thermal resistance by length of elect. insulator which is a heat radiator – Tony Stewart Sunnyskyguy EE75 May 7 at 14:39

For some brands its only aesthetics for other it marks what type of electrode spark plugs have. Also as far as I know Bosch green ones are replaced by blue ones.

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