Spent the past hour searching the forum for a discussion on this question. My confusion comes from the way this is written up in the owner's manual service schedule. It could be read to say that the O2 sensor should be replaced one single time, at 60K miles. But I feel sure that I've come across threads in the past that suggest it should be replaced every 60K. It's been exactly 60K on my 124 and, although I have no complaints about idling and there's never been a CEL or code for O2, if it's time for a replacement it's time for a replacement. Since we have no emissions testing in FL, it's up to each one of us to know when a replacement is called for. What say ye?

BTW, 199K miles on the clock. Last replaced @ 139K.

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1988 California version 260E (W124)
Anthracite Grey/Palomino
Owned since new and still going strong and smooth
MBCA member

Past Mercedes-Benz:
1986 190E Baby Benz
1967 230 Inherited from mom when she downsized
1959 220S Introduced me to the joys of keepin' 'em goin'

There are only 10 kinds of people in the world--those who understand binary and those who don't