Article, Spark Plugs Separating Fact From Opinion
 

Great Article on the various plug and how they do / do not behave.

https://www.dragzine.com/tech-storie...-from-opinion/

Pretty good article. I just went through this several months ago.

From my understanding, first there is an optimal temperature range a spark plug operates in, hot enough to burn off the carbon deposits and prolong life, but if too cool, fouling occurs, and if too hot, the tip of the plug melts. So engines are "matched" with appropriate plugs that will reasonably be maintained at that temperature range for various driving conditions / heat loads.

For my street vehicles, I've always stuck with manufacturers specifications an never had any problems, and get good life.

The problem I have seen is with power adders, turbo's, superchargers, and nitrous. In a racing environment, where the heat load is very high, you'll need to run a colder plug to prevent the plug from melting. And under the consistent high heat load, the plug stays somewhat clean. Unfortunately, if you street drive the vehicle as well, cruising, the plugs don;t see nearly as much heat, and the tips remain cooler, and over time, several thousand miles maybe, the plugs foul, and you lose ignition.

I think the iridium type plugs can operate cleanly at a much broader temperature range, mainly cooler temperatures, so you can run a cooler plug that will withstand high heat loads especially under power adder conditions, but will continue to run cleaner at low heat loads during normal street driving, as compared to standard tip plugs.