Why do stocks prefer hotter plugs? And why do certain setup use colder plugs? Could somebody give me the reasoning behind differnt temp sets on spark plugs. What setup should use what range and stuff. TIA

1995 Eclipse RS

I know you want the hotter plug especially if you make a lot of short trips. On short trips in traffic, the plugs use the extra heat to burn off more of the crusty deposits that accumulate over time. In traffic and on short trips, the engine is run up and down throug the rpm range and so the fuel mix changes enough to make for some quick deposit buildup. On the highway, or during long drives, the engine stays at a higher rpm for a longer period of time and the deposits that build up are able to be burned away due to the extended amount of time at temperature.

You don't have to run any hotter range or colder range when you're stock, it just helps to make your plugs last longer and make your engine more efficient imo.

Now, if you run higher CR or dump a ton of AF into the combustion chamber (turbo), you'd want cooler plugs (pretty sure) as the more you compress a gas (air), the hotter it gets. By using a cooler plug, you throw in some added protection against detonation.

I'm not sure what the actual difference is temperature-wise, but it canmake a difference in the right situation.

Hope I could help a little bit at least here!

^ Well said.



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