What Is The Difference And How Do You Know Which To Use?

 

A spark plug needs to hot enough to be self cleaning (burn off deposits) yet not be too hot that it causes the fuel/air mix to ignite before the spark plug fires. As you HP increases, you're more likely to pre-ignite your air/fuel ratio, therefore you run a colder plug than stock. There can be 6 or more heat ranges of plugs. I'm presently running two heat ranges colder than stock on my 10# blower car.

 

sweet thanks