I am not going to say that a plat plug won't work in MB engines. I will only say some may and some may not. My 500SEL DOESN'T like the plat plugs at all. If I have learned anything in the last 50 or so years working in engines is "Always Use The Plugs Called For By The Manufacturer" as they will ALWAYS work. Others may or may not. I would recommend you but 6 plugs of the correct brand/type called for. If you still have problems, then fix the problem and try the plats again if you like. If your engine is one that doesn't like the plats (like my 500) then the plugs will fix the problem. If you leave the plats in and try to fix the problem you may spend great amounts of money and never fix it.
A rule in my shop, I will not work on drivablilty problems unless the car has the exact plug called for by the manufacturer. If the customer has put in something else (or has had it done) and won't let me put in the correct plug I will just send him on his way. I would much rather him tell others that I wouldn't work on his car because it didn't have the type of plugs I like than either not make any money because of the time it takes to trouble shoot this type of problem or charge him for my time and get the reputation that I rip people off.

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84 500 SEL (307,xxx miles)