I had put the w9DC0 (0 on the end, bigger center electrode) and the car had a HUGE miss at idle-- 1984 380SL. I posted on that experience and complained to Mercedes who gives owners that plug. I even got Bosch on the phone with me and they agreed that plug could ause issues in my car. I learned this lesson the hard way. Yes in some cases some people have no problem switching up plugs to platinum or whatever. But I have experienced, and I have seen so have others, VERY EXPENSIVE troubleshooting efforts that in the end was a simple plug issue. I tell people to read the owners manual and use the plug originally recommended for the car period. There is no good reason to introduce the unknown of a different plug typically. Vor me it is a Bosch W9DC and after putting those back in the problem went away.