Re: Gramma's Car: the new project!
With NGK plugs, the higher the number the colder the heat range, i.e. 4 = hot, 5 = middle, 6 = cold.
I *believe* ranges 4,5 and 6 are the standard passenger car heat ranges for NGK's, you might have to upgrade to a premium or race plug to go colder.
FWIW, I was running UR5 plugs in my 496 and they were too hot. I've since switched to 6's which I am still currently evaluating.
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