Should I replace O2 sensors?

[Josh Harder]

So asked this question in the o2 sensor thread but got no replies.
Here goes again.
I bought 4 with the intention to replace them all. I went back to the previous owners records and noticed on of the downstream sensors have been replaced 8000kms ago. Should I bother replacing that one as well or just save the new one for when its needed? Keep in mind I have zero codes and engine light isnt on. Changing them to see if it will improve my terrible mileage and fix my long crank issue

 

[LJ Jim]

I would do all 4 unless you could verify the correct one is installed. Even then, if was easy to reach I'd swap it and keep the used one as a spare.

 

[Chris]

O2 sensors are general wear-and-tear maintenance items. All of them should be replaced every 80k miles or so, regardless of whether you think they are bad or not.

I would suggest replacing all of them, yes.

 

[Josh Harder]

Unless you know the brand, replace all of them.

Ntk sensor replaced at 193k. I'm at 199 now

 

[Daryl]

Ntk sensor replaced at 193k. I'm at 199 now

I wouldn’t change it then.

 

[Josh Harder]

O2 sensors are general wear-and-tear maintenance items. All of them should be replaced every 80k miles or so, regardless of whether you think they are bad or not.

I would suggest replacing all of them, yes.

I will replace the other 3 for sure