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I was looking at oxygen sensors for my vehicle on rock auto and found large price discrepancies. I saw sensors ranging from $25 up to $100. in general what do the more expensive sensors have that the cheaper ones don't?

For example, here is one which fits my Mazda 626 for $19 by an American company named Walker, a $24 NTK, and a $70 one from Bosch.

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In a word? Nothing. I mean, a 4-wire O2 is going to be about the same no matter what it's made for. The connector may be different, but the guts are going to be pretty much the same.

Unfortunately, you really need to know what works well with your vehicle. For instance, Bosch (from my understanding) originated the O2 sensor. Their product should be above reproach. They work well in most vehicles. For some reason they didn't work well in my 94 Camaro. This was a known thing amongst Camaro owners; it wasn't just internet hearsay. There are too many firsthand accounts of them going bad in our cars. The regular option were either ACDelco, Delphi, NTK, or (my favorite) Denso. These would last for a length of time you'd expect.

Point is, don't be afraid of the cheaper sensors. Ones like Denso are much cheaper than Bosch, but should provide you with the same service life. I don't think I would trust ones which you don't recognize the name. These are probably Chinese knockoffs. While the Chinese could be making decent O2's, their product quality/manufacturing practices have shown need for improvement. This is my opinion, though.

  • Funny, I've been reading allot of denso vs. bosch threads on bobistheoilguy and almost everyone doesn't like bosch aftermarket stuff. – Robert S. Barnes Nov 26 '15 at 18:42
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    @RobertS.Barnes - While there is a lot of good information on the "Bob" site, beware of the opinion masquerading as fact. Since participating on SE, I have grown a huge cyclical eye towards a lot of stuff on the Internet. – Pᴀᴜʟsᴛᴇʀ2 Nov 26 '15 at 18:47
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    @Paulster2 : s/cyclical/cynical/? – Zaid Nov 27 '15 at 10:46
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    Cyclical eye, sounds crazy. – I have no idea what I'm doing Nov 27 '15 at 10:51
  • @Zaid - I'll blame that on auto correct, lol, but "cynical" is definitely what I was shooting for there. Thanks! – Pᴀᴜʟsᴛᴇʀ2 Nov 27 '15 at 11:02
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In general what do the more expensive sensors have that the cheaper ones don't?

There is no functional difference; all 4-wire zirconia-based narrowbands should exhibit the following:

  • useful voltage range 0.1 - 0.9 V
  • stoichiometric AFR at 0.45 V
  • low voltage = lean condition, high voltage = rich condition

Certain brands may have a quicker warm-up time or response time to AFR changes compared to others, but the above-mentioned behavior will not change.


I imagine the difference in price will be due to a few key factors:

  • Different supply chains

    In my experience this has a huge impact on the final price that you pay. Don't assume that Brand A and Brand B are comparable because you're buying them from the same online retailer.

  • Brand premium

    Sometimes you pay for the name rather than the sensor. It's quite common to have the same sensor sold under different brand names (I've seen this with AC Delco and Denso).

  • Build quality

    I imagine that manufacturing tolerances and material quality can impact the response time and useful life of an O2 sensor. A better build will command higher costs that influences prices.

  • Intended operation

    All 4-wire sensors should functionally be the same, but the location of the sensor will influence factors like operating temperature. A pre-cat O2 sensor located in the exhaust manifold will experience higher temperatures compared to one that is located in front of the catalytic converter. The design specifications for these two locations could drive differences in the materials and manufacturing process that are employed, and might explain why certain cars don't like certain sensors.

  • Actually, that's not entirely true - you're talking about zirconia sensors exclusively. Some cars use narrowband titania sensors which operate differently - instead of generating voltage they vary their resistance while exposed to oxygen. That means the operating range will usually be different and lean-rich levels can be inverted. If you connect a titania sensor to an ECU designed for zirconia sensors or vice versa - it will not work or might even be damaged, as far as I can tell. – I have no idea what I'm doing Nov 27 '15 at 8:02
  • @IhavenoideawhatI'mdoing titania sensors are new to me. According to this article they're not so commonplace. Thanks for the head-up, I'll update my answer. – Zaid Nov 27 '15 at 9:45
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The other answers have covered most things, but here are two points that haven't yet been mentioned.

Warranty

This is usually a function of the supplier rather than the manufacturer, but some places offer a lifetime guarantee. Others offer none.

Physical fit

How hard could it possibly be to make accurate threads? Apparently pretty hard for some manufacturers who are not quite up to 21st century manufacturing techniques and quality control.

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At Rockauto, an upstream Denso O2 sensor for my Toyota Tacoma costs $107 with no warranty, while the same sensor from Bosch has at least a 12 month or more warranty and costs $127. I'm guessing you're going to have to pay more for a warranty. Read carefully the fine print with regard to warranty coverage, if there is any coverage at all.

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