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Spark Plug Heat Ranges

A Spark Plug's heat range is a measure of it's ability to conduct heat away from its firing end. A COLDER or 'harder' spark plug is more suited to a hotter running engine (i.e. high performance, high revving, tuned or driven very hard), the shorter heat path will conduct heat more quickly, ensuring that the tip does not overheat. Conversely, a HOTTER or 'softer' spark plug has a longer heat path and will maintain a higher tip temperature, carbon deposits are more likely to 'burn off' and the plug tip will stay cleaner.

NGK Denso Champion Heat Range

This is a *basic* table of approximate spark plug heat range equivalents from manufacturers NGK, Denso and Champion. Note that Champion have further additional heat ranges for different application types (e.g. Marine engines).

ngk denso champion heat ranges