Kalakov222

Once again, I have gone back to the books to revive my memory about spark plugs.
As I understand, Hot Plugs ie ones with numbers 7 onwards or so run hotter, thus better suited for regions where climate is cold year round e.g. northern Europe, Moscow, Siberia, Canada etc, so that the Combustion Chamber gets hot quickly and remains hotter.

Conversely a 'Cold Plug' designated by its number 5 etc would run cooler thus more well suited to all year round warmer climates.

Can anyone please comment to confirm or rectify my understanding.

BOTUS

plug temp has nothing to do with the ambient conditions - and the heat range can vary between manufacturers - with champion and ngk the exact opposite

plug temp is about the state of tune and the emissions - run cool enough they don't clog - unless you have turbos run funny fuel and have wound boost to death just buy stock plugs or iridium if you want an imperceptible benefit

Kalakov222

Thank you for that insight, can I badger you for some more light on the topic, Bosch says 7 and higher are HOT PLUGS. lower numbers are cool. What youre suggesting is that the Hot Plugs are meant for high compression chambers, typically Turbo charged Engines? Conversely this means Cooler Plugs would run better in naturally aspirated engines?

BOTUS

a given engine in a given state of tune needs plugs that run cool enough for the plug to survive (not cracking insulator or erosion)
and hot enough to burn off any despots that might build up and eventually impact ability to produce the spark
on a stock engine running stock fuel, used in typical conditions always use the manu recco plugs