Spark plugs heat range, What's the difference between 6,7 and 8 Options

[ST-204]

As topic

[97GTinKC]

The colder a plug is, the quicker it dissipates heat, too cold and they tend to foul, too hot and they can stay hot enough to pre-ignite the fuel, causing detonation (very bad thing) all ranges of a given plug have the exact same spark, so go with the factory or manufacturer recommended heat range for YOUR engine. and like he said above, forced induction needs colder plugs, as they tend to run hotter in the combustion chambers, unless you have turbo'd or added a supercharger or raised the compression, I'd use the factory recommended heat range plug.
One other comment, if you go with a different brand, look it up in their book. I used to work in an auto parts store, one day I looked up plugs for my car in the 5 top brands, then used the cross ref in each brands catalog to cross the others to an equivalent plug, out of 5 brands, I came up with 17 different plugs of various heat ranges...