Originally Posted by Sean05
WOW... on a sparkplug its not going to change anything... change it every 30k... even guys that tracks constantly dont replace it that often..
Sure it makes a difference. Many people are having them changed ~ 20k from other posters here. 37k is just the MAX you want them to go. Since I drive 4k/year, changing them every 4-4.5 years seems reasonable for leaving a plug in the head.