Avoid iridium, and platinum like the plague. Go with copper core at least, at best use what is printed on the sticker. The techs who fix these engines, will be on shortly(usually),to tell of the problems iridium, and platinum has had with these engines. Also change them ASAP, the plugs should be changed every 30000 miles. After 4-5 years, if you drive like my family your well past that.