One thing I have learned over the last 50 years of working on cars is that the only plug to put in an engine is the one called for by the manufacturer. There are exceptions like NGK BP5ES Bosch. This is really because the Bosch are harder to find. The exception above was learned when I needed some plugs and couldn't find the correct plugs so I went with NGK from advice of Mersedes Shop users. If I could find a good source of the Bosch I would still use them.

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84 500 SEL (307,xxx miles)