Graphite is an Abrasive.

Use

MB part # 001 989 26 51 10 "Lock cylinder Grease"


(And following WD 40 with H20 and Soap ain't a solution.)

I MIGHT use WD40 as a Flushing Agent ['Only thing it's good for] followed by
CRC Electrical Parts Cleaner (NOT AS Aggressive as Brake Parts Cleaner).
DRY.
Then the MB Lock Cylinder Lube.

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'84 300SD sold
124.128