Counterfeit Spark Plugs?

Discussion in 'Mechanical' started by CowboyTaco, Dec 3, 2019.

  1. CowboyTaco

    CowboyTaco Well-Known Member

    So I recently came across a post on another forum regarding counterfeit spark plugs coming from both Amazon and Ebay. Supposedly, it was only NGK that you had to worry about, but turns out the DENSO has become subject to these as well.

    I thought I bought my last set of spark plugs from the dealership, but turns out I got them from Ebay. Well, shit. So down the rabbit hole I went. Instead of writing everything that has already been written, here is a post from someone who does about as good a job as anyone at showing examples of fakes:

    How to spot counterfeit Denso Spark Plugs

    My key takeaways being that
    • there shouldn't be any bulging around metal engravings
    • engravings should be deep
    • the writing on the ceramic should be centered between the base and the first rib
    • "DENSO" should look like a slightly different marking than the model number below it
    • the plug end should be matte and not have any gloss to it
    • sleeve protector should be longer than the plug (i.e. protects the ground rod in addition to threads)
    • images printed on packaging should be crisp

    The fact that I even have to question this is annoying. I didn't know that counterfeit plugs were a thing.
  2. CowboyTaco

    CowboyTaco Well-Known Member

    My first thought was that it was odd that there was a pack of 6, but that didn't bother me. I just figured that the seller had purchased them in bulk and had a box that could fit 6 plugs. The packaging looks as close to genuine OEM as I've ever seen. In fact, the packaging gives me no suspicion of fakes.


    The Denso lettering is different than the model of the plug, so that would indicate legitimate. However, it is not perfectly spaced between the first rib and the metal base. Still not convinced they are fake.


    The protective sleeve is plastic, which is a good sign; however, it doesn't extend very far past the ground rod. The legitimate ones seem to be ~1/4" beyond the tip of the plug.


    Finally, the bulging around the "+" symbols. From what I understand, this isn't supposed to happen.


    So the lettering not being centered on the ceramic, the protective sleeve not being long enough, and the bulging on the engraving makes me think that I picked up some fakes. Can anyone convince me one way or the other?

    I have not checked the gap yet, but I believe they are supposed to be .40. I'll check that as soon as I find my gap gauge.
    Last edited: Dec 3, 2019
  3. CowboyTaco

    CowboyTaco Well-Known Member

    Here is the stock image from Napa. The spacing on the wording looks more even and I don't see any bulge around the engraving. upload_2019-12-3_11-47-13.png
  4. Oswego

    Oswego n00b

    Thats scary!!!

    Glad I always buy from Toyota dealers direct. Even then that fake stuff can still wiggle its way into the supply chain with one bad apple.
  5. AlienXtx

    AlienXtx Nignog

    I get all my plugs from the local NAPA, but I've never paid much attention to the lettering.I just checked my stock and all I have on the shelf currently are motorcraft for my small V10 buses. But heres what the plastic looks like on them, it's about 1/4 past.
    Anathollo likes this.
  6. CowboyTaco

    CowboyTaco Well-Known Member

    Yeah. I'm kicking myself now. Looks like I'll probably be ordering some from Advance as they are on my way home and doing a 25% deal right now.

    Also, the writing is centered in the porcelain. Hard to see through the plastic, but looks like there is no bulging in the engraving.

    I contacted the seller this morning to ask for a refund. We'll see what happens.
  7. CowboyTaco

    CowboyTaco Well-Known Member

    Ok, so I purchased 6 new DENSO plugs from Advance Auto Parts last night on my way home. I need to get a side by side comparison, but so far they are looking pretty similar. The engraving on the metal still has bulges in some spots, the lettering isn't perfectly centered on the porcelain, and the plastic sleeve - while longer - doesn't extend down much further past the ground rod.

    The ebay seller also said I could send them back for a refund, but that shipping would be on me. Maybe they are legit...or maybe someone else bought legit plugs from AAP and returned their Chinese junk in the legit boxes...I'll compare them all tonight.

  8. Oswego

    Oswego n00b

    Is there any sort of resistance test that can be done to them?
  9. CowboyTaco

    CowboyTaco Well-Known Member

    Not that I'm aware of.

    I emailed DENSO prior to Thanksgiving to see if there were any "sure signs" that they could clue me in on. I finally got a response yesterday stating that there is no guide and that I should only buy from reputable sources.

    ....thanks, Denso....:(
  10. PSU Taco85

    PSU Taco85 Well-Known Member

    I’ve found the cheapest to be on rock auto. I have a set I bought a few months back to save on shipping from a previous order. I’ll grab a few pictures tonight.
    Taco Loco likes this.
  11. tx_shooter

    tx_shooter You ever try to roughie a bear? Staff Member

    You would think they would be a bit more aggressive against counterfeits.
    Anathollo and PSU Taco85 like this.
  12. PSU Taco85

    PSU Taco85 Well-Known Member

    I ordered 6 denso from rock auto and this is how they shipped them to me. A 4 pack and 2 singles.

    2BE6DDDA-0EFB-4E7C-BF27-A99E200174B6.jpeg DF6AE0C4-3879-475B-B99D-D2ECA0275234.jpeg

    The label looks pretty centered, no bulging on the + sign that I could tell
    13B31E9C-F807-4586-8749-3F4862569531.jpeg 91AD4EB3-6FFD-4641-B0A5-85D72F1698D5.jpeg

    The sleeve extended about 1/4” below the electrode.

    CowboyTaco and tx_shooter like this.
  13. CowboyTaco

    CowboyTaco Well-Known Member

    Not sure why the first pic got rotated. Either way, plugs are lined up exactly as they came out of the box withe the part number facing me. Them all coming out of their respective packages the same orientation is a good sign.


    For all pictures, Advance Auto Parts on the left and Ebay OEM on the right.

    You can see that neither of them have good spacing on the porcelain. The "N" is slightly rubbed off from the ebay "OEM" plug. Not all of them are like that, just the one I happened to grab for the sample.


    The next 2 pictures show the engraving quality. The one from AAP is "better" in the sense that it doesn't bulge as much, but both of them have bulging around the engraved (or maybe imprinted?) letters/symbols.



    The AAP plug shows "DENSO OD LP" around the ring, while the Ebay plug reads "DENSO JAPAN LC." I have no idea what it should say, so this is kind of a wash to me. Sadly, the DENSO rep has been less than helpful. The crush washer appears to be much thicker on the AAP plug.

    not pictured: I pulled another from the AAP set that says "DENSO OD GB" on the plug. Holding the plugs up closer side by side, the AAP has a much taller nut portion than the Ebay OEM one.


    Finally, the protective sleeve is about the same length on each.


    So at this point, I'm still at a loss for what I should think.
    Last edited: Dec 5, 2019
  14. Taco Loco

    Taco Loco Tired and Lazy, married to ‘The Laundry Fairy’

  15. CowboyTaco

    CowboyTaco Well-Known Member

  16. Taco Loco

    Taco Loco Tired and Lazy, married to ‘The Laundry Fairy’

  17. CowboyTaco

    CowboyTaco Well-Known Member

    again, not concerned about whether they will spark. are they genuine?
    tx_shooter likes this.
  18. Silverback

    Silverback I'm not always a dick. Just kidding, fuck off.

    Does Denso have multiple factories to make these things in? May just be a matter of different lines producing different results but both are genuine.
    TacoXpo likes this.
  19. Taco Loco

    Taco Loco Tired and Lazy, married to ‘The Laundry Fairy’

    you have to much time in this, just buy from reputable stores and return the ones to the store that you think are fake, lol it’s unlikely we would end up with them.
    TacoXpo, AlienXtx and PSU Taco85 like this.
  20. Silverback

    Silverback I'm not always a dick. Just kidding, fuck off.

    This belongs in the tin-foil hat thread. :D
    AlienXtx likes this.

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