Naturally you should change the oil asap, and refill with whatever weight is proper for your climate (if it's really bad, maybe change it twice).
Seeing as how the oil was never changed, I bet the airfilter is filthy too.
I would also suspect that the PO used cheap gas...so you might want to throw in some decent injector cleaner.

Then I would see how things stand after that.

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It is a truism that almost any sect, cult, or religion will legislate its creed into law if it acquires the political power to do so. Robert A. Heinlein


09 Jetta TDI
1985 300D