What kind of sparkplugs 1994 e420

The issue, as I understand it, is not that the plug is platinum. The issue is that all Bosch platinum's are resistor plugs, and the MB ignition system is designed for a non-resistor plug. In theory, the OEM non-resistor plug is going to give you a higher quality spark than the resistor platinum plug.

Will any copper plug suffice?? Thank You!:)Nel

As long as it is non-resistor, and meets OEM specs, it should. Personally, I just run the OEM recommended plugs.

No.

You need the correct BOSCH plug because of the different way Mercedes does the resistance thing. There's an NGK equivalent that some people say works even better. But those are your choices. No other ones will work properly.

bottom line.... if originally there were copper (ie non resistive) plugs installed then you can put any old 'copper' (ie non resistive) plugs in there..... it just doesn't matter what brand. You see, in the distributor there is about 1k ohm resistance and in the boot (the part going over your plug) there is another 1k ohm resistance. Now you can addd more resistance via platinum or other 'resistive' plugs (ie they have resistance build into them) and they 'will' work.... however not as well since the spark 'timing', because of the extra resistance in the RC ignition circuit, will cause a slight but important delay and, more importantly, the spark will last too long and is consequently weaker since energy is conserved.

cheers, guenter

the 1994 e420? I have no owners manual as I just bought this car. Thanks again! :)Nel