Thanks Helmut thats some good info. I learned something anyway, I always thought a hotter or cooler plug had something to do with the spark. Which leads me to another question, having a plug thats "too hot" damage your piston? I'm sure I was told this at some point in time and really don't know if its true especially now after reading that.
Yeah, if the spark plug heat range is too hot, it can cause overheating.
"Overheating will cause the electrodes to wear quickly and can lead to pre-ignition. Pre-ignition will dramatically raise the cylinder temperature and pressure and can cause serious and expensive engine damage. When inspecting a spark plug that has experienced overheating or pre-ignition, blistering on the ceramic insulator and/or melted electrodes can sometimes be found."
The paragraph quoted above was taken directly from the NGK website. So yes, pre-ignition caused by overheating, will raise the cylinder temperature and pressure and could very well damage the piston.
