The actual sensor for an oxygen sensor is inside the opening "gills" of the sensor. I have read that it really doesn't make sense to try and clean them and in fact there is usually a big disclaimer about getting any of that dielectric grease on the oxygen sensor body. So i would never spray them with anything! Heated sensors are only supposed to last 60,000 miles and unheated ones for 30,000 miles so you might be better off just replacing them . BTW the generic Bosch ones work just as well as the BMW specific ones although you may have to splice in your own connector off your old one.
I would just replace it if it is suspect.
Last edited by Flotsam; 06-13-2012 at 05:45 PM.