Dry graphite is best and what experienced/knowledgable locksmiths use (and have far more experience with locks than a MB technician). I've used graphite for years with no failures. However, why don't you call your local MB service dept. and ask what they recommend so we will all know.
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1977 300D: 300,000+ miles
American Honda: Factory Trained Technician & Honor Grad.
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