Gentelmen

I have seen many posts recomending not to use Bosh Platinum 4 plugs. But most of these were in response to people having trouble with getting there engine started or rough idel ect. I have been using Bosch Platinum 4 plugs in my 1988 560SL for about 5000 miles now and so far it starts and runs well. Since I put these plugs in the car as soon as I got it I have nothing to compare it to. I went to the platinum because it was a newer technology than what was available in 1988 and they work so well as standard equipment in both my Fords where I change plugs at 60,000 miles wether they need it or not. So far the Fords never really needed the plugs to be changed at the 60,000 mile interval. All I can say is that Bosch platinum 4 plugs do not make my car hard to start or idel rough. But I cant really say anythigh good or bad about them. So what are the issues. Does anyone have any real A to B comparisons of plug usage with real good fully functioning vehicals.

I do know plugs can make a difference. In the early 80's I found that there was a noticable difference in the idel charicteristics of Toyota's with Nipondenso vs champion plugs. Nipondenso being noticably smoother.

Also aside from platinum 4's what about straight platinum. My car calls for a Bosch W9DC0. I have currently installed 4479's, What about W9DP's.


John Roncallo

Mercedes has a technical bulletin out about the platinum plugs. Says not to use them. Not sure what engines it covers since my diesels don't have to worry about that issue.

Len

The issue is really RESISTOR versus NON-RESISTOR plugs. Merc and Audi and some other German OEs us NON-RESISTOR spark plugs. Now if you install resistor plugs you change the voltage wave form at the electrode, which can lead to driveability and idle quality problems and can also cause higher emissions when tested in the field. Since many older Mercs don't have a lot of margin on emissions you don't need to install a part that may increase emissions.

Since very few modern cars use non-resistor plugs, they can be hard to find at McParts, but Mercedes parts specialists like Fastlane stock correct OE non-resistor Bosch replacement plugs and can have them at your doorstep as soon as the next day.

I tried the Bosch single electrode resistor type platinum plugs that I bought at McParts for less than two bucks, each in my car back in the late eighties, and they increased idle roughness and emissions. I now will only use the correct OE replacement Bosch Super copper core, nickel electorde NON-RESISTOR plugs - H9DC.

Multi-electrode plugs are junk. All that cold metal (relative to flame front temperature) is a good way to quench an insipient flame. It's pure marketing BS and may actually degrade engine performance and increase emission due to greater misfire frequency.

Duke

I cant rember who posted this link (was it Kestas?) but I found it interesting enough to bookmark.

http://www.robertstanley.biz/firestorm.htm

This might be a little off the topic of this thread (not directly related to platinums vs coppers...) but I thought it might be a good place to get some feed back on it and get it a little exposure.

Edit: So as to actually contribute to the point of the thread... If you run coppers (at about ¼ the price) you could change them more often and have cleaner plugs and less siezed threads... though the right amount of anti sieze prevents that as well.

__________________
-Marty

1986 300E 220,000 miles+ transmission impossible
(Now waiting under a bridge in order to become one)

Reading your M103 duty cycle:
http://www.peachparts.com/shopforum/831799-post13.html
http://www.peachparts.com/shopforum/831807-post14.html

Does anyone have a copy of this bulliten

Thank You
John Roncallo

I think the non resister Bosch plugs run about .90 cents each. Just buy a set and see if you notice a difference. It could be an interesting experiment.

Since I have a diesel I don't follow this, but I was always told to use copper non resister plugs in MB's, unless it is an M112/M113. The newer engines use the long life platinum plugs like everyone else.

__________________
1999 SL500
1969 280SE
2023 Ram 1500
2007 Tiara 3200

The spark plug wires have a 1K Ohm resistor in them in the end connector. Thus adding a plug with more resistance you are actually taking away spark. Also increasing chamber temps due to the hotter spark of the Platinum 4 plug. Some have no issues, others cars will not run smooth with them. But in the end you want a non-resistor plug for the older Merc's so you get as much spark as posssible.

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~Jamie
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2003 Pewter C230K SC C1, C4, C5, C7, heated seats, CD Changer, and 6 Speed. ContiExtremes on the C7's.

1986 190E 2.3 Black, Auto, Mods to come soon.....

Here's my (recent) experience -
I bought my 96E320 last summer, with just under 50k miles. It had been driven very little the prior two or so years (100mi/mo ? +/-).

I took several driving/sightseeing 1000 mi. roundtrips, getting used to the car (and it to me). The highway mileage, using CC @ 74-75 mph, was consistently 25mpg...right on the EPA hwy. estimate.

I recently had an independent shop which had been maintaining the car for the prior owner perform the recommended 60k mi. service, which included the installation of new plugs which I'd already bought - the Bosch double electrode plugs.

I've taken one 600 mi. R/T since that servicing and got just over 27mpg for the trip. (I also had the formerly rather noisy rear Michelin XGT's shaved just before the trip...waht a difference in ride and noise!)

So, I don't know if the new plugs are responsible for the rather dramatic increase in hwy mileage, but it would seem so.

Opinions?

If you had only changed the plugs you could safely attribute the better mileage to them. But by doing the 60K service and shaving the tires you introduced additional variables. Also, did the recent trip follow the same route as the previous trips?
Mark

The 600 mi R/T was similar, and I even nudged the cruise control up to 77 - 78 mph for most of the drive. (I've also been maintaining 32F/34R tire pressure with the new, accurate gauge I bought.)

Slightly mysterious results, but pleasantly so with premium now at $2.40 in my near environs.

I've also noticed about a 1 mpg bump with my around town driving...this despite the fact that I've recently been accelerating much harder to the posted limit than I was doing the first months I owned the car. (Maybe I've adapted to how the car prefers to be diven.)

At any rate I spent in excess of $400 for this "routine" 60k maintenance (a first for me with nothing amiss with a vehicle) but feel I got some direct, however small, payback.

I use the oem Bosch copper that originally came on the car and change them every year. They cost something like $15 for the 6 plugs. I have heard that the original plugs work the best in the older cars.

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1989 300CE Astralsilber/Schwarz
1992 300CE Schwarz/Schwarz

Thank you to all the people who replied, some good experiances here. I guess I'm just going to have to experiment.

I happened to check my owners manual today and it recomends Bosch W9DC or W9DP. However I cannot find W9DP's anywhere. Boschusa.com recommends:

WR9DP Platinum resistor plug
4479 Platinum +4
4307 Platinum 2
W9DC Super Plug copper
W9DC0 O.E. spark plug
7511 Super part
4220 Platinum Part

Has the W9DP been droped from poduction? It seams to be banished from the face of the earth.
How can I tell if the 4 diget code Bosch plugs are resistor plugs or not? I cant find a decoder for this series of plugs.

John Roncallo

Fastlane has the W9DC's and a couple others.

If you see the letter R in the plug code it is a resistor plug. No R in the code no resistor. I think NGK and Champion are the same.

__________________
1999 SL500
1969 280SE
2023 Ram 1500
2007 Tiara 3200

If you are interested in trying a new product, why not consider:

http://www.nology.com/silver.html

For your car it's the S5 plug.

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1989 300CE Astralsilber/Schwarz
1992 300CE Schwarz/Schwarz