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Originally Posted by Roncallo
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
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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