...the differences/ advantages of "cooler" or "hotter" spark plugs.

For example, a lot of guys (including me) use the autolite 3923, which is "cooler" than stock.

Do "cooler" plugs give better power or MPG?

Do "hotter" plugs give better power or MPG?

 

I believe cooler plugs are better because an engine that is cooler performs better. I guess

Here this website has some good info on spark plugs http://en.wikipedia.org/wiki/Spark_plug

 

Hello,
I am the technical manager at Autolite spark plugs. There is no advantage to going to a colder spark plug on a unmodified engine at all. The engine calibrator spends tons of dyno time choosing the very best heat range for performance. If you all want to really understand all about heat range, when to change and when not to, use this link and watch video number 5.
http://www.autolite.com/learn_more/a...elect_region=1 If you have any questions, I am happy to answer through the forum or at jay.buckley@honeywell.com