I'm curious as to how many miles this SD has.

You are more likely to see a drip mark under a 617 than not - they like to mark their territory.

Can you tell which side of the engine the leak is at? Personally, I would suspect a leak on the passenger side, but your pictures are from the drivers side.
Just in case you are still reluctant to get a new cap, .....yes, get a new cap, then take it from there.

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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