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How to spot counterfeit Denso Spark Plugs: DENSO 3426 Iridium Long Life FK20HR-11 2018

Hi everyone, I recently installed a set of what I believe are very well made counterfeit spark plugs in my 2007 V6 AWD. I did the plugs because my gas mileage was horrible, and surprise surprise installing counterfeit plugs did not improve the mileage! I'm installing the real plugs tomorrow and hopefully that will solve the problem.

Anyway.. I had a very hard time identifying the fake plug, because the counterfeiters have adapted to the existing guides to identifying fakes very well!

Here is the existing offical DENSO guide to spotting fakes: DENSO SPARK PLUGS

You will see in my album that the counterfeiter has adapted!


>FAKE: Terminal has a glossy finish.

My fake did have a slightly glossy finish but no more so than my used genuines.

>FAKE: Marking - Printed wording can be scraped off.

My fake could NOT be scraped off, the printing was very high quality.

>FAKE: Housing -Poor surface finish.

My fake had very good surface finish

>FAKE: Screws & Electrode - Poor thread quality finish.

My fake had very good thread quality.

Also another existing guide: https://www.driven2automotive.com/blog/how-to-spot-fake-denso-iridium-power-spark-plugs-2017/

>FAKE: Electrode is copper/gold colored, not iridium colored

My fake had a grey color instead of copper, looking MUCH closer to iridium. However it was not as SHINY and had no BLUE HUE like real iridium.

So, I have made this image album to show you how I decided I had fakes after comparing to new genuines purchased from a major auto supply store: https://imgur.com/a/Kz3nT

These pictures contain 2 Real DENSO plugs, 1 with 100k miles and 1 new. The fake was installed and run for about 150 miles.

1. FAKE: Bolt surface ~1mm shorter/thinner than genuine. In the pictures you can see that both red lines are the same length, but the fake is only as thick as the blue line.

2. FAKE: Electrode wrong color. Very convincing color however not as shiny or blue as real iridium.

3. FAKE: Electrode slightly too large, genuine electrode is very slim. Fake electrode is the right shape and very convincing, but very slightly thicker.

4. FAKE: Gap out of spec. DENSO 3426 plugs are gapped .040-.044 from the factory. My fake plugs came with out of spec gaps. Should have been an alarm bell!

5. FAKE: DENSO JAPAN engraving on metal jacket between threads and bolt is thin and weak. REAL engraving should be bold and deep, although you can see variation between the two genuines.

6. FAKE: + markings seem to be cut into metal jacket, leaving very slight BULGES in the metal around the crosses. REAL crosses appear to be lasered or ground in and result in NO bulges although it is hard to tell from the pictures.

7. FAKE: DENSO lettering is bold and solid colored. REAL DENSO lettering is actually not a solid texture, but instead displays a cross hatching texture as seen in the photo on the 2 left plugs, both real.

8. FAKE: Terminal is slightly glossy. REAL terminal will be matte and not glossy. VERY subtle and hard to tell in the photo.

In conclusion, if you don't want to run the risk of chinese fakes on ebay or amazon, buy from a reputable auto parts dealer. Even then, if you don't get it from an authorized Toyota Dealership, feel free to give it a check for these telltale signs.

Hope this helps anyone, good luck!
 

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Agree with DL175. Unless there is a fault or material in the spark plugs which shorts the discharge current to ground internally so that it does not fire at the electrode there probably would be no improvement in gas mileage. Modern ignition systems use very high voltage for spark ignition and will fire even plugs which are out of gap spec. with the gaps being too large. Plugs need to be replaced when deposits build up on them from use which can short circuit firing - ordinarily quite a long time with today's gasoline.
 

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Don't be surprised if the real Denso plugs will not improve fuel economy.
Agree with DL175. Unless there is a fault or material in the spark plugs which shorts the discharge current to ground internally so that it does not fire at the electrode there probably would be no improvement in gas mileage. Modern ignition systems use very high voltage for spark ignition and will fire even plugs which are out of gap spec. with the gaps being too large. Plugs need to be replaced when deposits build up on them from use which can short circuit firing - ordinarily quite a long time with today's gasoline.
I won't be surprised, since I am getting very cynical about it haha. OTOH the original plugs are 110k old and pretty worn out, so fingers crossed. Either way, I'll be happy to not have fakes in there.
 
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