By on March 22, 2016

jaguar-S-Type, Image: Jaguar

John writes:

I recently had a local shop confirm the need for O2 sensors in my Jaguar S-Type. With 97,000 miles on them, it seems very likely they need replacement, and the mechanic wants to install factory sensors at the cost of some $650 for the parts. I can purchase Denso or Bosch from the local parts store for less than $200. As these parts were originally designed to last at least 80,000 miles (Federal warranty requirement), I figure that replacements from any reputable source will last quite a long time.

What is your opinion as to brand specific parts versus more generic replacement parts?

I suspect the original supplier was actually Bosch anyway so in my mind they are the same.

Sajeev answers:

Your last sentence is my usual go-to statement, especially as cars depreciate to the age of any Jaguar S-Type. I still remember cringing when my trusted mechanic, some 15+ years ago, said my father’s Mark VIII’s (not the one I currently own) intermittent fuel smell was from leaky injectors. The replacement injectors cost $800, and they were a unique part number with no aftermarket alternative.

Perhaps that’s what he thought since it was the first Ford with that particular engine, but it was all bullshit: all Fords with that engine use the same 24 lb-hr injectors. I grabbed my Ford Motorsport catalog and ordered a set for $275-ish, delivered to the shop, and crossed my fingers for a seamless install. Thank goodness I was right.

Back to the “value” of factory vs. aftermarket parts on a heavily depreciated motor: it really depends. Factory body parts? Yes. In this case? No, get Bosch O2 sensors and pocket the extra cash.

Forget about the price, odds are they are the original equipment manufacturer (OEM) anyway. Sometimes you’ll even get a factory part when buying the “aftermarket” brand: happened to me when purchasing TRW control arms and several HVAC parts. And it’s nice to see those factory castings, part numbers or packaging when you’d never pay for them. It’s kinda like poppin’ tags, sort of.

When do you buy OEM bits, Best and Brightest?

[Image: Jaguar]

Send your queries to [email protected]com. Spare no details and ask for a speedy resolution if you’re in a hurry…but be realistic, and use your make/model specific forums instead of TTAC for more timely advice.

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42 Comments on “Piston Slap: The Cat’s Meow for OEM or Aftermarket Parts?...”

  • avatar

    I actually manage a commercial auto parts program and can tell you in my experience that the Bosch sensors have a higher failure rate and are more likely to be an incorrect part, even when specified as an OE sensor. That part is probably just my computer catalogs being stupid and incorrect but the failure rate is definitely higher. I recommend OE first, and then denso or NTK (made by NGK after that). I’ve never had an issue with a denso that I can recall. Stay far far away from universal sensors too.

    • 0 avatar

      I agree in full. I installed Bosch O2s on my old Mazda MPV and fuel economy seemed to consistently be a bit lower than it was before. A switch to Denso O2s corrected the issue. It seems that Japanese cars are ‘happier’ with Japanese-brand O2 sensors, perhaps European vehicles work better with Bosch brand sensors? I’ve had decent luck with the ‘semi universal’ sensors where you need to wire the 4-pin plug yourself, but the sensor itself is the correct shape/style as the one being taken out.

      • 0 avatar

        I’ve had parts guys and mechanics tell me the same thing about ignition components for Japanese cars as well. Even if Bosch or Champion has the equivalent parts, I’ve never not gotten a strong recommendation to stick with NGK.

      • 0 avatar

        Denso has been OEM supplier to Jaguar for climate control and engine management for quite a while. On Jags from the 90’s and 2000’s I’ve never run across a Bosch part on them. Don’t know about the new stuff. 80’s Jags use Bosch EFI stuff rebranded as Lucas.

    • 0 avatar

      Agreed. I’ve had nothing but grief with Bosch sensors, and not just of the O2 variety.

    • 0 avatar

      In defense of Bosch, well sort of, on my old VW everyone was running NGK plugs instead of the original Bosch. I got my hands on the parts book and saw that the NGK was a cooler running plug than the Bosch. So I got me some cooler Bosch plugs and yea they ran better. Now to my point, I wonder if someone like Denso saw how to improve the original sensor?

    • 0 avatar

      I will second NTK or Denso over bosch. This is is also an advantage of buying from the so-called aftermarket. You can choose your supplier. The oe just buys from the cheapest bidder anyway. I remember there was a period of time that Champion plugs were coming in OE Mercedes boxes

      • 0 avatar

        I recently bought a box of AC Delco spark plugs, the recommended part number from the OE supplier, red white and blue, for my Caddy. I even bought them at a local non chain parts store.

        Plugs come out, and on the back of the box, at the very bottom, in block letters “Product of Germany”. They looked like the OE plugs that came out, but those said “Bosch” on the insulator….

        Oh well. I really tried to Buy American….oh, and these plugs, wherever they come from, live under Denso coils. I agree that the car was ASSEMBLED in the US, anyway.

        Buying OE is getting a known quantity. I’ve learned over years of BMW parts buying that the BMW part is always right, at twice the price. The OE supplier, if you can get it, is the same part at a “normal car part” price. Then, there are knockoffs. Avoid-especially any rubber parts…the rubber in any bushing or mount is special and the results of a lot of R and D, not just out of a catalog in China.

        I’ve bought replacement parts for the BMW where the only difference is you can see someone has dremel-tooled off the BMW logo.

        A professional will always go OE, because they know it fits, can return it if they get a bad one, and can make a profit on the part costs overall. I don’t mind paying for labor, but I do dislike paying double for a part.

  • avatar

    I truly hate it when an O2 sensor goes bad. The check engine light comes on, everything seems fine, but that Amber light just annoys you.

    • 0 avatar

      Big Truck,
      Such problems as the Amber messing with you should be corrected asap, perhaps if the light said hellcat or perhaps a picture of a jar of Gray Poupon you would approve? I

      I am fine with skipping OEM if you go for quality aftermarket parts and that seems the case here.

  • avatar

    I would check the model specific forums. This is usually the best bet. I would definitely go aftermarket thou. Likely one is the actual OEM anyways. I’ve mentioned it before but I did a job for a former CEO of a German parts maker . He told me how it works and he laughs every time he see’s the internet tell people to buy OEM sensors (in this case for BMW and Benz) over the one branded with his companies name, since they were actually the same thing.

  • avatar

    Denso for sure. They work first time and are as likely as Bosch to be OEM. You would be amazed how many Ford products use Japanese origin parts due to the Mazda connection of that era, into the current day. Bosch may also have been OEM but their aftermarket line in my experience isn’t up to the same standard as the OEM line. The same can be said of Denso on occasion bit you wouldn’t know it since both parts work flawlessly.

  • avatar

    I’m going with Sajeev’s “it depends”.

    I went with some Chinese axle shafts for my Subaru, because they were $100 a side, as opposed to $400 a side from Subaru. Put them on, and every time the car would come to a complete stop in gear, the whole car would vibrate violently.

    Looking online, it’s a known issue with knock-offs transmitting every bit of engine vibration through the whole car. Spent $1k on the Subaru part, issue solved.

    But other things, like brake rotors, I’ll take Chinese all day long. My old rotors were $85, now they’re $12. I don’t care how garbage they are, I can replace them with the pads at that price

    • 0 avatar

      Brakes wouldn’t be my first choice to save a buck with sweatshop made knockoff parts. Best of luck to you.

      • 0 avatar

        Ehh, I’ve been using cheap as possible brake parts since the mid 90’s with no ill effects. I see the potential but so far no issues.

        • 0 avatar

          I bought a set of Brembo pads for my MDX. They came in a nice box with a hologram and everything. Tossed dust like you would not believe and lasted 10k. Record Grooved the Disc, too. Turns out Brembo does not make brake pads for my truck…..
          I replaced them with OE pads, which were correctly shimmed, unlike the fake brembos, and luckily are happy with the grooved discs.
          My $15 Centric pads on another car, however, bite like semimetallics should, and aren’t killing my discs.

          • 0 avatar

            For non-track applications, I heartily endorse Akebono Pro-ACT pads.

            They are ceramic, but bite nearly as good as good semi-metallic pads, so they hardly dust.

            Akebono also makes many high quality, OEM (true OEM, put on at the factory) pads.

      • 0 avatar

        It’s a solid piece of metal, and on a street car. Worst I would expect is they warp easier, but I haven’t even noticed that yet.

    • 0 avatar

      “I went with some Chinese axle shafts for my Subaru, because they were $100 a side, as opposed to $400 a side from Subaru. Put them on, and every time the car would come to a complete stop in gear, the whole car would vibrate violently.”

      My brother has seen many Subarus come through his shop like this. The owner drives with cracked boots spewing grease everywhere until it starts to burn on the exhaust manifold, they go to a shop that says “easy peasy, we’ll slap new axles in” rather than offering to re-boot the OEM axles, and these vibrations are what you end up with. best case scenario is catching the OE boots when they just tear and before potential bearing contamination, but my bro has re-booted even very far-gone looking OE axles and has never had a come-back.

      • 0 avatar

        Yeah I have rarely had an issue with other brand CV joints going the cheap off rock auto etc route. Subaru ones seem to have an issue however and must be carefully sourced. I have used Napa branded ones twice without issue, and they were quite a bit less then the OEM and seemed to hold up with out vibrating unlike the cheap auto zone and china special ones. Your mileage may vary as I’m sure NAPA switches suppliers form time to time. (at the time the NAPA route was suggested by an old school mechanic friend who was one of the first US certified Subaru dealer techs back in the 70’s)

      • 0 avatar

        GTE, a mechanic who reboots instead of replacing is awesome in my book. BTW, this is a typical problem in german auto land as well. If a cracked/torn CVJ is the problem, rebooting is the way to fix it. If you do enough of them re-greasing the cage is not messy or hard. In terms of parts costs, we are talking about a difference of $25 v. $250 per side. And you don’t have to worry about whether the shafts are hollow (good) or solid (vibration issues).

        • 0 avatar

          He’s actually figured out a slick little trick for these re-boots where he can separate the axle at the joint, leaving the one halfshaft sitting in the transmission. He can bang out a re-boot job on a Subie in no time at all, it’s pretty amazing stuff!


      • 0 avatar

        They did actually offer to rebuild them, I don’t remember what the prices were, but I just decided to go all out with new OEM after the first set up failed. I did keep the originals for rebuilding if the new Subaru parts didn’t work out, I’ve still got them in the garage to this day even, but the new Subaru parts worked like a charm.

        You’re probably right, the rebuild would have done the trick, but this was also in the middle of me spending way too much money proactively replacing basically the entire suspension before a long trip, as I’d just decided to keep it as a daily driver for a few more years and it was at 175k miles on all original parts. At that time a “rebuilt” anything wasn’t appealing, and I wanted new parts. You live and learn.

    • 0 avatar

      There was an “investigative journalism” exercise that looked into cheap Chinese-made brake parts. They found that the cheap pads were not pickled to prevent corrosion; rather, they were simply painted black. The friction material was not up to OEM standards. In some cases, the friction material would separate from the pad, rendering one wheel ineffective for stopping.

      While I have not heard of any total brake failure due to cheap overseas components, I certainly would not use them in any demanding application.

  • avatar

    I agree with checking the vehicle forums thought but many of those will suggest OEM manufacturer parts only. I have had excellent luck using Denso O2 units on American and Japanese branded vehicles across the board—others may like Bosch or alternate brands better.

  • avatar
    Felix Hoenikker

    I’ve replaced oxygen sensors on two Fords and 1 GM car with after market Denso and Bosch sensors. They all worked perfectly

  • avatar

    With O2 sensors? The forums can tell you who probably made the originals. That said, a well-installed universal (if available for this application) can do just fine; once you have the correct number of wires, the only difference between O2 sensors is the length of the cord, and the harness connector at the end (which often has some integrated resistors in it.)

    With parts in general? Again, you really have to hit the forums; for some parts, some generic thing direct-shipped from China off of eBay might work fine, for others, OEM might be the only decent one available.

    Absent any specific guidance, go with larger, well-known manufacturers that have a healthy OEM business. Stay away from no-name cut-rate Chinese parts unless you have specific information that it’ll work well. I also try to avoid unknown-source parts, like Auto-Store brands or Beck-Arnley; they are WAY too hit-or-miss. Sometimes you’ll get an OEM or really good aftermarket part in the box, other times it’ll be generic junk.

  • avatar

    In the Jeep world (XJ’s and TJ’s) I have always been advised to stick with MOPAR or OEM parts when you can get them. HOWEVER, if those parts were eye wateringly expensive like you mentioned then I wouldn’t. Bosch sensors have a poor reputation in Jeeps, everyone I know has gone with NGK in the end. As long as you avoid generic brands you should be fine.

    • 0 avatar

      I second the problems with Jeeps. On the WJs only OEM sensors and electronic parts work on them, yet they are the parts that keep failing. Funny I have an old Jeep (01) and an old (BMW). Both around 90 k miles. Between the 2 the BMW is cheaper to maintain.

  • avatar

    Only one data point here, but I just dropped less than 50 bucks on a Denso O2 sensor (right bank, front) for our LS430 and it did the trick. Factory sensors were going for about 150, but the one that came out of the car was manufactured by Denso.

    What’s not to like? evidently out on the Lexus forums there was word of counterfeit Densos being sold, but a trained eye could spot the difference.

    I got mind from ^m^zon, figured it would be the real deal, and I guess it was.

  • avatar

    For many years NTK has been the OE supplier to Jaguar for O2 sensors. Generally, Jaguar parts are reasonably priced, but for some reason O2 sensors are crazy expensive from a dealer.

    Just get NTK’s off for $29 each and your car will be happy. Same part, different box.

  • avatar

    On my ’91 Mercedes Benz 420 SEL, I find Bosch replacement parts are EXCELLENT…if not better than, the originals. Save a few bucks, and go for it.

  • avatar


  • avatar

    As an anecdote, in 1985 or so, one headlight burned out on my ’83 Mercedes 300SD. I went to the dealer and the service writer told me to buy one from the parts department and the porter would install it, to save me a bit of time. I bought the bright blue/white “Genuine Mercedes Benz Replacement Part” box for $18, opened it up and inside was a GE sealed beam bulb which, at the time, went for $5 at Pep Boys. I use aftermarket parts, only if they don’t say “Made in China”.

  • avatar

    When replacing knock sensors on my Lexus RX300…I had real problems with the aftermarket ones …after two failures, I went with the factory ones the short factory wire harness and have had no issues in the last 25K miles.

  • avatar

    Chrome mirror caps and HiD sez that’s a later S-Type R.

  • avatar
    Kyree S. Williams

    Plus, it’s Bosch. It’s not some no-name outfit you’ve never heard of (which, itself, probably wouldn’t be the end of the world). Buy them.

  • avatar

    My Mazda 5 had quite a few suspension issues early on. I replaced all the Mazda stuff that had issues with non OEM stuff. No problems in the 25k since most of the work done, on PA’s awful roads with mostly city driving.

    I’ve found that every so often, the OEM stuff is the best bet. The rear wiper on the Mazda 5 is a Mazda only part, all the aftermarket blades don’t work well, leaving a large area uncleared. It’s worth the $20 every two years for the properly functioning part.

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