Cold Plugs, Hot Plugs, Red Plugs, Blue Plugs

[N40GL]

Is anyone aware of a simple reference to the difference between these 'colder' spark plugs, and 'hotter' spark plugs, or something that can explain the temperature ranges and why one or the other is better (or worse)? I think I understand this, but I want to know more. Call me an 'info-maniac.'

[fastblackmerc]

Found this on the NGK website:

http://www.ngksparkplugs.com/techinfo/spark_plugs/overviewp2.asp?nav=31000&country=US

[RF Overlord]

Man from U.N.C.L.E.:

Think of it this way: a "cold" plug is one which conducts more of the heat of combustion away from itself and into the head. A "hot" plug is the opposite. It retains more of the heat.

Neither plug is inherently "better"...it depends on use. A motor that is lightly loaded will usually use a hotter plug to prevent combustion deposits from forming on the tip and electrodes. A high-performance engine will use cooler plugs to prevent pre-ignition. Bear in mind that these are guidelines, not hard and fast rules.