I use NGK's Iridium heat range 8 (BKR8EIX)..... they run great and lasted alot longer than regular coppers. My first set lasted about 30,000km before I started getting slight misfires. Replaced the plugs at about $8/plug and it runs great again. I don't recomend heat range 8 for non-turbo cars though, stick with the stock heat range which I think is 6.