Funny you should post this now.. I have about 1,000 miles on my plugs.. and they finally had juice applied yesterday.. they rode around in the car that long! Knew what fun it was going to be.. and wasn't dissapointed in the least..lol.. 3 hours later (last 45 in the dark) I was done.. Idles smoother..but other than that.. I'm guessing at being 77,000 miles someone else has changed them out..but can't swear to it. Looked really good on the old plugs.. but maybe chemtool and lucas have something to do with that. All I can say.. at least there was very minimal blood loss over it! I love my Miata.. especially at plug change time.. LOL..