Iridiums do not last as long as they claim. I just changed out my Iridiums I had in my car for 60,000 miles and they were garbage. I've learned my lesson and will just stick with stock copper plugs, and change them every 30,000. I was under the impression that the densos were supposed to last 100,000 miles but I'm glad I didn't put them to the test. stick with stock plugs.(I'll post up some pics later of what they look like after 60,000 miles of abuse.)