WHY ARE THERE DIFFERENT HEAT RANGES?
It is a common misconception that spark plugs create heat. They don’t. the spark plug heat range only indicates the rate at which the spark plug dissipates its firing end heat to the engine.
Selecting a spark plug with the proper heat range will ensure that the tip will maintain a temperature high enough to prevent fouling, yet be cool enough to prevent pre-ignition. While there are many things that can cause pre-ignition, selecting a spark plug in the proper heat range will ensure that the spark plug itself is not a hot spot source.