Book on this one says change em at 100K oh its still a little peppy, and idles nice, but my mileage is suffering now. I get 23.5 combined city highway with a twin cam 2.2 Ecotec engine. I used to get 28 combined city highway when car was new. No fault codes bad sensors etc. Its time. Autolite double platinum plugs arent expensive thru rock auto when shippings combined with parts i need for other car projects.