If the bolt was in good shape I don't see how a 6-point socket would round it off. I would try vice grips next. Failing that, I would get a new oilpan if its easy to replace on that model.

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1985 380SE Blue/Blue - 230,000 miles
2012 Subaru Forester 5-speed
2005 Toyota Sienna
2004 Chrysler Sebring convertible
1999 Toyota Tacoma