Heat ratings on spark plugs

[thexav]

What do the heat ratings mean on spark plugs and how would I decide if I needed a hotter or cooler one?

Is it right that a highly tuned engine needs a hotter plug to take the heat out of the tip more efficiently? (Or is that what they mean by a cooler plug? I'm totally confused on this one!)

 

[HDi fun]

I'm pretty certain that a colder plug would be fitted if the standard ones are overheating. They transmit heat more effectively away from the plug nose.

Therefore a hotter plug is used if the plugs foul excessively in whatever normal use the car experiences.

With modern materials you're probably fine in standard road cars using whatever standard plug is listed for the car. I have had good results with Japanese Denso Iridium plugs in the 528i. Only changed 'em once and this set can allegedly be left alone for another 60,000 miles. Which is good from a servicing cost point of view.

 

[SLEEPER]

colder plugs for higher tuned engines.

or you could remember it as hotter engine colder plugs.

Colder plugs are particually important on turbod cars as they run extra hot.

 

[HDi fun]

Supercharging will always increase cylinder and combustion chamber temperatures. Colder plugs are essential