Grease not oil
I don't think oil is heavy enough use the heaviest grease you can get. to do it properly you should remove them. In that case just replace them. Very easy to do. Remove the door panel and it is a four bolt job. I always use the appropriate type of 'loc-tight' for reinstall.
1982 240D 313,000 (4 speed)
1984 300CD 172,483
1985 German Shepherd Dog -Lacey- R.I.P.11/04/05
Hood Stars, Wrist Crowns and Obsession Dobs