If you look at my pics on my vacuum pump seal change on a previous tread I did just that I put it all around the outside edge and a little on the O ring as TampaMark said it helps keep the ring in place for install.
Just be sure to not get any on the inside if you do clean it out. While you are doing it I would change out the oil sending unit that is right under the pump. Since the pump is out it will so much easier. They seem to start leaking about the same time.
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