[Subix]

I had replaced both of mine at the same time (165,000) and both of them looked like they severely needed to be replaced. (throwing code 32, running rich, smelling gas).

I didn't notice an improvement in gas mileage but at least it's operating fine and not throwing codes or killing me with gas fumes. I would say replace them before they inevitably fail if your just looking to do some preventative maintenance.