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1997 Mercedes 600 Coupe & 1995 500 Coupe, 2004 Yamaha R1 200hp 360 pounds
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Discussion Starter #1 (Edited)
I am going to be replacing all my plugs and I was wondering your opinions on which is the best bosch plug. The one on the right was from the dealer and has a thicker electric tip where the one on the left is also OEM with a thinner tip but I got a lot cheaper from a parts place. Are they the same or what are the differences. Sorry if the pics arent clear I tried to get a better shot of the tips.
 

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Can you post the part numbers for the two plugs? The part numbers should be stamped on the side of the round part of the body, just above the seat where the thread starts.
 

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1997 Mercedes 600 Coupe & 1995 500 Coupe, 2004 Yamaha R1 200hp 360 pounds
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Discussion Starter #4
ones on the left are fr8dpp33 and the ones on right are F8DC4
 

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At the Bosch website, they only list one spark plug for your vehicle, and that is the Bosch 7422 (aka FR8DPP33), when using their Part Finder online utility. Bosch recommends a gap of 0.032". It is critical that the plugs are not gapped any larger due to the ignition system used in your vehicle, at least not initially when establishing a baseline. Notice even Bosch doesn't recommend their own multi-prone plugs for this vehicle.

Bosch : Error

I suppose if you don't want to take any risks and just want to fall back on the original copper plugs, there isn't anything wrong with it. However, the Bosch 7422 is a double sided platinum plug and will give much longer life. In addition, there is more potential for the Bosch 7422 to give better performance.

If it were myself, of the two, I would choose fr8dpp33 over F8DC4.

Personally, I would clean the threads in the spark plug holes until I can screw in the plugs with a light consistent finger pressure. And install the plugs without any anti-seize nor friction-modifier compounds. Torque the plugs to spec's with an accurate torque wrench. However, in your case, I would even exam the threads closely if possible. Sometimes one of those cheap 1-million candle power flash light comes handy to focus a powerful narrow bean at the threads. But it is not always easy since there isn't enough room to do so, so you may have to be a little creative.

http://www.boschautoparts.com/Resources/FAQS/SparkPlugs.htm
 

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2009 SL65, 1998 CL600 (sold), 1989 560SEL (sold)
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According to the MB EPC, F8DC4 is correct thru model year 1997. For cars built after 1998 it lists BERU '14 FGH-8 DPURX 2'. I've checked some of the online parts suppliers and the Beru plug is hard to find. A few list the Bosch FR8DPP33 as equivelent.
 

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There r certain parts at the dealership, that r worth paying extra for. I would say most certainly for electrical components like spart plug wires, cap and rotor etc.

Go with the dealer plug. It looks like it is better manufactured.

And I would sugggest u replace them all at the same time. Costly but easier to monitor.
 

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1997 S600 (sold)
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Go with the dealer plug. It looks like it is better manufactured.
As far as I know, these are both "off-the-shelf" Bosch plugs. Not really anything that Mercedes has any influence on regarding quality of manufacturing.

Generally speaking, there is nothing wrong with copper electrode plugs. They're quite good. Use 'em. You don't have to "go platinum" because it sounds high class. Put copper in your spark plugs, and put platinum around your finger. :)

Brett
 

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According to the MB EPC, F8DC4 is correct thru model year 1997. For cars built after 1998 it lists BERU '14 FGH-8 DPURX 2'. I've checked some of the online parts suppliers and the Beru plug is hard to find. A few list the Bosch FR8DPP33 as equivelent.
Bosch's website lists only one spark plug for both the 1997 and 1998 S600. autohausaz.com lists the same coils and connectors for both the 1997 and 1998 S600.

Often when a part reaches end-of-life, a replacement is recommended by the manufacturer. F8DC4 and FR8DPP33 are very differently designed plugs. I can't comment on the quality of the FR8DPP33, but I have used the F8DC4. Clearly it is not of a modern design and the quality is similar to the cheaper copper plugs. The higher end plugs such as the Platinum+4' or the newer Fusion, or the NGK and Denso iridium plugs are of better quality than the F8DC4.

For the ignition system type used in the S600, the fine wire plug with a single grounded electrode can provide better performance than the traditional copper plug, especially when it comes to durability.

I will side with Bosch on this one. Technically, their recommendation makes sense.
 

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As far as I know, these are both "off-the-shelf" Bosch plugs. Not really anything that Mercedes has any influence on regarding quality of manufacturing.
Brett
With the quality-WAR still being raged among the car manufacturers, I don't think Bosch can afford to not be concerned with qualty. The Platinum+4's and Fusion's are high quality plugs. Bosch doesn't need Benz to influence them. Bosch has NGK and Denso to worry about. I would venture to guess that currently Bosch's biggest worry is in not having a competitive design rather than that of quality.
 

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I installed the Bosch Fusion 4 prong platinum plug with iridium tip. Car runs great. Super plugs were in and gapped correctly and looked fine. I believe the car starts easier and runs better by the butt meter. Definitely not worse.
With the quality-WAR still being raged among the car manufacturers, I don't think Bosch can afford to not be concerned with qualty. The Platinum+4's and Fusion's are high quality plugs. Bosch doesn't need Benz to influence them. Bosch has NGK and Denso to worry about. I would venture to guess that currently Bosch's biggest worry is in not having a competitive design rather than that of quality.
 

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M120, M119, W126*2 + Silver Avantgarde wagon
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According to the MB EPC, F8DC4 is correct thru model year 1997. For cars built after 1998 it lists BERU '14 FGH-8 DPURX 2'. I've checked some of the online parts suppliers and the Beru plug is hard to find. A few list the Bosch FR8DPP33 as equivelent.
This is correct for MY 1998 cars you need the Beru 14FGH-8 DPURX 2.

Not the Bosch. Just confirmed with MB USA. :wink

Can anyone advise why that may be?


Of note I just found out my production date was December 1997, so I am also fortunate mine is a late MY 1998 car...
 

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1999 S500; W140.051
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I think the expensive change was to an Iridium plug. The Beru cited is of that type. Reason for change may have been longevity of service as Iridium plugs last a very long time; easily 30-40k miles if engine is running well.

I do think the tiny electrode does provide better arc'ing at lower voltage as well.

There is an NGK cross-ref for plugs that can be bought for ~$8 ea. I've been using the NGK Iridiums for about 10 yrs and really like them even for older cars.
 

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M120, M119, W126*2 + Silver Avantgarde wagon
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I think the expensive change was to an Iridium plug. The Beru cited is of that type. Reason for change may have been longevity of service as Iridium plugs last a very long time; easily 30-40k miles if engine is running well.

I do think the tiny electrode does provide better arc'ing at lower voltage as well.

There is an NGK cross-ref for plugs that can be bought for ~$8 ea. I've been using the NGK Iridiums for about 10 yrs and really like them even for older cars.
Very helpful, and interesting - thank you.

It becomes such a time consuming hobby looking after these M120's, or even just researching all the details of how to look after them...

I'll be heading west soon - hope to have a W140 meet up at some point...?
 
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