Hello All,

I have a 1997 965, and I am noticing the fuel mileage is not what it used to be. I suspect it is time to change the oxygen sensor(s). My guess is that theses need to be changed in pairs. If I am wrong, which one is the likely suspect?

Regards

 

I'm not familiar with that car in particular, but if it only has 2, then one is the 'upstream' sensor, and one oi the 'post-cat' sensor. The post-cat sensor does nothing but tell the ECU that the catalytic converter is in place and functional. The other is what relays fuel mixture information to the ECU.

 

Check codes. It will tell you which one is bad.