they say?

[cascadeclear]

I just bought a 1990 535i. It seems to run fine. They say you should change your o2 sensor out every 60000 miles or so. Is there a way to tell if it is starting to go bad? It passed emission test just fine. Should i just change it out? what are your thoughts?

[CarDriver]

If it is OK, I would not change it just for the heck of it. It runs about $125.00. you can find the cheaper but I would not go for the $60.00 ones.

[bimmer dot info]

If the O2 sensor is still working just leave it till the check engine light comes on.
If you can get a bosch for 60 go for it. The cheap ones are typically just the sensor with leads so you will need to splice them to the old connector from your current sensor.
Looking at autohaus there were 2 sensors for your car. One is a 3 wire and the other is a 4. I think the generic 4 wire ones work for either one but the 3 wire is only $71.