Marlon said:This is a good thread on spark plugs - made me decide that standard plugs changed regularly is the way to go http://www.z4-forum.com/forum/viewtopic.php?f=2&t=84273&p=1249444&hilit=spark+plugs#p1249444
nfbr said:I use NGK iridium and change them every two years despite only doing 1-2k miles per year.