how a hot spark plug works
How Spark Plugs Work This can lead to pre-ignition, knocking, and permanent engine damage. If you aren't sure which spark plug heat range to use, err on the side of using a plug that's too cold rather than a plug that's too hot. Hot plugs have more insulation and are found in most standard engines. The extra insulation keeps the plug's temperature high enough to burn off carbon deposits, which allows for more time between spark plug changes.