What 02 sensor lite???

[Myke456@aol.com]

All this talk of 02 sensors has me wondering why I've never seen an 02 sensor
light thru all 190,000 miles (orig.owner) on my 87 5kcsTQ with original
sensor. My 84 5k had one, but i figured they eliminated it. So - 2 questions:

1) My impression is that the warning lite, if present, is a reminder to
change it for emission monitoring purposes only-is this correct?
2) Does the sensor effect performance?

Thanks for your help guys.

Still looking for 15",5 lug wheels,
Mike Aiello