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They came from the factory with double platinum, non-resistor plugs.

Everything out there is a resistor replacement, though.

The Bosch 7422 is the closest thing to the OE plug.

Get the wrench tool to remove the plug wires and follow the DIY in the stickies, it's pretty straight-forward. I'd also suggest testing the ignition wires while you're replacing the plugs, you can just buy singles to replace any that test bad.

Good luck.
 

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Interesting. I haven't come across the distinction between resistor and non resistor plugs before--even in the sticky section. I've seen other plugs recommended--such as ngk-7090. What ill effects would one see from using a resistor plug?
 

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Interesting. I haven't come across the distinction between resistor and non resistor plugs before--even in the sticky section. I've seen other plugs recommended--such as ngk-7090. What ill effects would one see from using a resistor plug?
Bosch started making all their plugs resistor a few years back so in my bikes I had to switch to NGK or change the resistor plug wires on the bikes.
 

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I just found them a couple of months ago -- and entirely by accident. All of the info in the stickies predates that.

Resistance approximately equals reduced energy, and since they came with NR plugs originally and the ignition wires measure higher resistance than on other makes I've owned, I decided I was going back to what MB originally threaded in. Whether it will make any difference I don't know, but I will be due for a change next year and would rather put back what should be there. I just have this idea that the folks who designed the engine specified NR plugs for a specific reason, and I think they probably had good reasons for doing so.

BTW, the NGK 7090 is a single-platinum plug. The originals were double-platinum, and the double in this context refers to the two electrodes, the center and the side, not those multi-electrode things that don't often seem to play well with these sequential-fire engines.

NGK makes a double-platinum (resistor-type) plug for this engine, but it's lots more expensive than the Bosch 7422. There are already a few threads discussing it.

As with anything else, we all need to make up our own minds about how best to maintain our cars. For me, generally speaking, I'm happy to defer to the guys who designed and built the thing. Well, other than that whole "sealed" transmission hogwash. ;) :p :D
Nothing wrong with putting back what came with it. However that would mean that on my '72 280SEL I would have to use bias ply tires, dino oil and asbestos brake pads.:)

Technology advances and one with careful consideration should take advantage of it.
 
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