Think of it this way.. it'l make it real easy. It is NOT that actual way it works and makes NO real sense... but its easy to think of it this way if you don't feel like actually understanding it.

Ok so imagine your running 30% nitro right? Oh no! More nitro = a hotter engine! I better get a colder plug to cool it down!
vs
Im running 10% nitro. Oh no! My engine is running too cold! I better get a hotter plug to warm it up!!

Im running 20% nitro. Hmm.. well.. that's juusst right.. lets throw a medium plug in there to keep it happy.


There is my crazy way of thinking about it.