[ma71supraturbo]

toulene/xylene shouldn't affect the life of O2 sensors as they are simple hydrocarbons -- but yes running rich, burning oil, or running leaded gas -- will all shorten it's life. Some guys replace them every 30,000 miles, I believe the book specifies 60,000. I know of a couple cars with 180,000+ miles what appear to be original O2's


The TSRM procedure for checking an O2 sensor:

 

[ma71supraturbo]

It should definitely show lean when you abruptly let off the gas and coast in gear over 2000rpm