Hi guys,

So there is a lot of information/misinformation about which spark plugs to use in different climates. I was just wondering if you can clear that up for me, I'm rather confused by it. I live in southern Ontario (Canada) just a bit south of Toronto, so it does get cold here in the winter.

I'm looking at replacing the spark plugs on my G35 Coupe 5AT with the NGK Iridium spark plugs, but there are #5, #6, #7, and #8's available. From what I gather, #5 is closest to stock, but should I be looking at the others? My car is basically stock, but I will be adding a MotorDyne 5/16" copper isothermal spacer, Stillen Z-tube, Rev-up airbox, and K&N drop-in filter. I do not plan on doing anything else to the car other than an Osiris tune after everything is installed.

Any insight here would be great, thanks!

 

Spark plug heat range has ABSOLUTELY NOTHING to do with ambient temperature. It doesn't matter if it's 120F or -20F the temperature inside the combustion chamber is the same. Get the stock heat range.

The reason they make lower heat range plugs is for when you have higher cylinder pressure (turbocharged, supercharged, nitrous, etc) which creates more heat. You run a "colder" plug to keep from melting them due to increased combustion temperature (more air means more fuel means more heat). You don't want too cold of a plug though because it will foul out quickly.

 

Thanks! That's what I thought, but just wanted to include that information just in case.