Before you give up, I would continue to try the vice grip method and at the same time have an assistant try to force a thin blade of some type ( like a paint scraper , thin blade screwdriver) in between the drain bolt and the pan. Maybe once you get it started a bit, it will screw out.

Taking the pan out will be a pain in the ass. As a last resort you could clean the surfaces well and use RTV sealant to stop the leak. Then use the "pump out" method for future oil changes.

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1994 E320 Cabriolet
1992 300CE (Sold)
1991 300SE (Sold)
1986 560SEL (Sold)