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

That was back in the days when the longevity of O2 sensors were questionable and California was pushing for cleaner cars...smog?

Now days if they fail you get a check engine light.

Bosch still suggests a 100K life.....BUT in real life "most" live about 150K.

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MERCEDES Benz Master Guild Technician (6 TIMES)
ASE Master Technician
Mercedes Benz Star Technician (2 times)
44 years foreign automotive repair
27 Years M.B. Shop foreman (dealer)
MB technical information Specialist (15 years)
190E 2.3 16V ITS SCCA race car (sold)
1986 190E 2.3 16V 2.5 (sold)
Retired Moderator

i think you will feel better if you replace it. However, must people would say, if it is not broken don't fit it.

OK, thank you. I will leave well enough alone for now. I'll get around to hauling out the multimeter one day and take some O2 sensor readings to see what it registers.

__________________
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

Does the accuracy of it degrade though affecting performance and fuel economy?

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2016 Monsoon Gray Audi Allroad - 21k
2008 Black Mercedes E350 4Matic Sport - 131k
2014 Jeep Wranger Unlimited Sahara - 62k
2003 Gray Mercedes ML350 - 122k

Yes...the resistance and values will change possibly sending erroneous signals to the computer. They will stay within value for a while as they weaken but it's typically not a "working/not working" issue. If you don't replace it, symptoms may arise leading you to think there is trouble elsewhere. Best of luck.

Interesting. I guess I will take some readings so that I know what's going on with the sensor. If declining fuel economy is a symptom of a degrading O2 sensor, I have that. Thanks for pointing that out.

__________________
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