How often do you replace the Oxygen sensors on your car? (vehicles, gasket)
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I have NEVER replaced a O2 sensor on any of the 6 cars Ive owned over the years.
Ive seen stuff like this on many websites:
Heated three and four-wire O2 sensors on mid-1980s through mid-1990s applications should be changed every 60,000 miles. And on 1996 and newer OBD II-equipped vehicles, the recommended replacement interval is 100,000 miles. A good oxygen sensor is essential for good fuel economy, emissions and performance.
or
Generally speaking, your oxygen sensor should last somewhere between 50,000 and 60,000 miles. However, if your engine is properly maintained, the sensor(s) may last much longer, up to the life of the vehicle.
But I have 260K on my Taurus with the original O2's and have never got a engine light for them or any of my other cars.
So is this a part that should be replaced as general preventative maintenance or if it aint broke dont fix it approach?
They either work or they don't. No point to replace early. You can test them with a multimeter to see if they've gone bad and are the culprit should a related CEL be thrown.
I see no reason to replace unless it's a scheduled maintenance item in the owner's manual. With the check engine light and OBD2, it's easy enough to determine when one needs replacing.
Even on my old 82 Scirocco, where the factory recommendation is to change the single wire unheated O2 sensor every 30K miles (with a reminder light on the dash, which is driven by a simple gearbox in the speedo cable) - I have over 100K on the current one, and as far as I can tell, it still works fine (judging by the CIS "frequency valve" buzzing rhythmically at idle) The last time I changed the O2 was after a head gasket failure (antifreeze will "kill" them pretty quick, from what I read) I have read that gas today is cleaner with lower levels of various impurities, particularly lead, I have read that early unleaded usually had some low level of lead in it, from being handled around leaded gasoline in the same refinery. I don't know if that last is true or not, I don't have a reference handy.
I have read that they do degrade in performance over time, and that replacing them "by the book" will keep your MPG and performance up - but I am getting over 40 MPG on summer non-ethanol gas, not sure I can really expect better than that.
O2 Sensors can function within limits less than the trigger set point for being "bad" in the OBD2 computer in a car.
But they can and do get "lazy" or function at much less than optimal for the emissions/fuel economy of a car.
IMO, best to replace these pro-actively on most cars. If the manufacturer's schedule is 100K miles, I'd replace them even if they haven't set a fault code.
We've seen significant improvements in fuel economy in a lot of cars that didn't have a check engine light on. For years, we used to take pictures of our o'scope readings on the O2 sensors ... so our customers could see the difference in a known "good" cycling system vs the old O2 sensors in their car. I believe that an o'scope is a far better diagnostic tool to reveal this electronic function than a voltmeter; we used an old 502A textronix (cheap ... all over the place for $100) for this and many other electronics diagnostics on cars (such as showing alt diode faults for cars "eating" batteries).
PS: Mitch ... the CIS frequency valve will "buzz" no matter what the O2 sensor signals are that feed the computer. There are two issues under control here ... emissions and fuel economy. Your car can be delivering very good fuel economy which you can observe, but absent a tailpipe reading with a 4-gas analyzer ... you don't know the other side of the equation. Could be getting good fuel economy but have a lot more emissions than it could otherwise deliver.
i tend to not replace parts unless they break. as for O2 sensors, i have seen too many people replace theirs and they work fine for a few months, and then they are told they need replacing again. that tells me the original sensors were working fine, but the mechanic got lazy and only pulled computer codes and jsut replaced what the code says was being affected, instead of running the necessary tests to find where the real problem was.
but i also agree the sunsprit has a good point. sensors do get lazy from time to time, which is why if you think you have a problem, you need to get a code reader that also shows the live data stream so you can actually see if the sensor is out of range or not.
My understanding is that they can get lazy. So, if one monitors mpg over the years, and notices a downward trend that can't be explained away, it may be time. One can hook up a scanner and watch the waveforms, and see if it looks lazy.
I've had to replace one, once. My VW TDi blew its turbo and apparently the heated O2 sensor didn't like oil. Had to replace it ($150? ouch). Worst part: it didn't do anything. I had the EGR removed and tuned to turn it off, thus it did nothing. But darned if it didn't test the heater circuit!
Knock on wood, 138k or more on all my O2 sensors, nary a problem.
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