What does the heat range of a spark plug indicate?

The heat range of a spark plug indicates the thermal characteristics of the plug, specifically how it transfers heat away from the firing end. A spark plug with an appropriate heat range can effectively dissipate heat generated by combustion while avoiding overheating. This is crucial for maintaining optimal engine performance and preventing issues such as pre-ignition or spark plug fouling.

The thermal characteristics determine how the spark plug behaves under different operating conditions. For instance, if a spark plug runs too cold, it may not reach the temperature necessary to burn off deposits, leading to fouling. Conversely, if it runs too hot, it risks damaging the spark plug or the engine itself. Therefore, selecting the correct heat range for a spark plug based on the engine's specifications and intended use ensures efficient combustion and longevity of both the spark plug and the engine.