I'm sorry, I should have clarified what I was saying. Copper is more conductive than the others. To make a long story short a copper plug will perform better than an iridium or platinum. The advantage iridium and platinum have over copper is that they dont wear as quickly and need to be changed. I forget which is a longer lasting plug, but iridium is more conductive than platinum so I would ASSume that platinums would last longer than Iridiums. I will never use anything autolite makes in a car again. Their quality is quite poor. What they say on the site is all true, but one thing to note is that while it does keep the performance close to new a longer time, that performance is still less than a coppers performance.