Hello,

I checked on ngk.com, and the part locator gave me this copper plug for my 97 SL500: BKR5ES.

But that's a resistor type. Does anyone know the correct NON-RESISTOR NGK part number for my engine?

Thank you!

With the exeption of Bosch, I have not found a readily available line of non-resistor plugs for Mercs. Fastlane can have you a set of proper plugs in a couple of days.

Duke

W9DC0 on your chassis has been changed to F8DC4 , Bosch Super , copper core , non resistor.
NGK replace is BCP5ES..

Here is cross charts

http://www.clubplug.net/bosch_ngk.html

I had the wrong numbers listed on my previous post, so I deleted it. I had 560SEL's on the brain I guess.........
Corect plug WAS F 9DCO, but Arthur is correct it was changed to F8DC4. Back when the car was newer, ie "in the day", the other recommended plugs were BERU 14F-9DUO, or Champion C12YCC
Gilly

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Thanks for the correction, Gilly..

I might add that I had done a few NGK copper changes from the F8CD4 as a kinda experiment on two of my personal cars , and the findings were excellent for the first 5K miles , but after that they started to have problems at idle.. I went back to Bosch and no more trouble after several Ks.
I also tried NGKs partner NTK O2 sensors and did find them to be better than the Bosch. I did scope comparison charts and found them both faster and cleaner , and am awaiting longevity results...

Thanks guys for the PN. But if anyone's had trouble with NGK's, I've heard that there's a difference between US-made and Japan-Made ones. When I used to ride bikes (I'm a UJM fan), my friends swore on the Japanese NGK's.... But UJM's are cheap, and my SL is no toy to screw with, so I just might stick with Bosch unless I hear any testimonials for Japanese NGK....

I just can't leave NGK's alone....

What is the difference between NGK's BCPxxx vs. BKxxx ? From their chart (goto http://ngk.com/sparkplug411.asp and click on "Manufacturer's Numbering System NGK" at the bottom of the page):

B = 14mm thread diameter
C = Hex Size 5/8"
P = Projected Insulator Type
K = Hex Size 5/8" Projected Tip (ISO)

Does that mean BCP = BK ? Well, the BK5ES doesn't exist in their catalog, so I'm guessing that the designation between BCP vs. BK is based on whim at NGK....

I had some problems with the early Bosch made in India.. [ the insulators actually spun in the hex case ].
I got 2 bad out of 6.. when I brought them back, I thought the parts guy was going to give me a hard time , but he just took them and said, ' Yup, we know all about it " and handed me 6 new ones ..
I guess the new ones are OK, but I still try and get ones made in G.

The "K" type have some different dimensions than standard types and need a special compatible boot.

Why don't you just buy the proper Bosch plugs instead of trying to reinvent the wheel?

Duke

While maybe you can find ngk plugs for the car, I agree it is not worth the trouble. NGK recently changed their part numbers by the way, making all of this only more confusig. Plus the parts feed to the auto parts store and their own website has errors. Buy the Bosch plugs SPECIFIED IN YOUR OWNERS-MANUAL. If you do not have it go to the Busch USA website and look it up. Do not just use whatever comes from the dealer and their parts feed, the bosch website is a more reliable source believe it or not based on my experience. MB has changed some plugs for the worse. For example, if your original plug is not large electrode (no 0 on the end of the part number), do not change to large electrode as MB might suggest. I get the feeling you are trying to solve some other running problem such as rough idle. If so maybe you could post on that.

Actually, I just can't leave well enough alone. Plus, I have a soft spot for NGK's.

Btw, as Arthur & Gilly says, the part for Bosch changed from F9DC0 to F8DC4. And the Bosch website's part finder lists the new F8DC4 for my car. So which should I do? The old with the "0" or the new with the "4" (Extended insulator nose)? And why did they change the recommendation to the colder heat range?

The F8DC4 run best in lean burn SFI engine
If you are stuck on NGK, go put them in .. but buy the Bosch F8DC4 at the same time so you will have them in hand a few miles down the road as I tried to explain to you..
There are tons of plug post in the archieves that witness the far superior running of F8DC4 on HFM/SFI benz engines ..and to the point that FastLane does not even bother with giving any other choice...as these have proven to suit BEST.
But,...From you NGK persistance , I think that our attempts to help you will not change this and that you have no choice to staisfy yourself but to buy-them, try -them, change-them..
Been there...done that..Good Luck..

Well, I just pulled my plugs, and have some pictures to look at. Please see thread:

Could you please look at my spark plugs?

Thanks!

I ran the NGK BCP5ES plug gapped at .032 for 12K miles and checked the gap. The results were very clean plug the wear had the gap out to .036. the recommended chnge interval is 15 k miles. average mileage 24mpg hwy at 80 mph.

http://ngk.com/results_fitment.asp?pid=bcp5es

I got em for 1.29 at Advance auto.