Exactly, the OEM setup is for resistor wire, not plugs.

the OEM wire harness incorporates the resistance in the connector at the plug end. MB does not use resistor wire.

why are you needing to replace them often?

My 1986 300E is on it's second set ever.

I believe factory wires are Beru and not bosch.


Michael

For whatever it's worth, I run a Bosch OEM wire set bought from Autozone and Bosch H9DCO non resistor spark plugs bought from peach parts. The rotor, cap, dust cover and ignition coil are all Bosch and were purchased from MB directly. The only part of the ignition system that isn't Bosch is the module, which is Siemens. With these, my M103 runs like new. From my own experience, I'd say Bosch is the way to go, regardless of whatever the cars had when they were new.

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Streetside: 1987 Mercedes 300E Petrol Blue/Green
2014 Ford Mustang Grabber Blue
1999 Ford Ranger Green

Dockside: 1968 Eltro 17
1985 Silverton 34C