There seems to be a lot of varying opinion on when to change these out. Through various posts i've seen as early as 60k and as late as 120k. Obviously if you're not having problems or throwing codes it's not something you think about much, but just curious and hoping to shed light for everyone. Mine's an '04 w/ 55k, so I'm hoping this isn't issue for me for some time.

 

They start losing their effectiveness as early as 60 K. Rover says replace them at 85K