Originally Posted By: mightymousetech
There are also two different types of Iridium plugs, just like platinum plugs. You can get them with copper ground electrode or platinum ground electrode. Make sure to get Iridium with platinum ground electrode if you want long life.
Just ran into this exact issue for my own car, on the NGK website, they have iridium and platinum plugs listed. The one actually listed as "platinum" is actually an iridium with the platinum ground.
I'm pretty sure you'll find most platinum and iridium plugs have a copper core ground. You probably think the copper is the exposed electrode. That is not the case. It's in the core of the ground electrode. Iridium and platinum are just the very tip of the electrodes. Anything that is not iridium or platinum on the exposed electrode is likely nickel, which is good at resisting hot corrosion.