Iridium Spark Plugs
Posted: Thu May 21, 2009 12:53 am
Been toying with the idea of getting one and was deciding between Denso and NGK. I got a little concerned when I saw that the NGK's heat rating was a "7", while the Denso's was a "22". Did a little legwork, and it turns out that they use different numbering systems for this value. Additionally, both of these manufacturers use ascending values for colder plugs, whereas other manufacturers use descending values. Here's a nice cross-reference from NGK's website:
