The oil pressure light on the bug (which is a she but still has no name) had been going off. Changed oil. Changed to different oil viscosity. Listened to the mechanic explain to me (after a few people had already expressed this opinion) that it was probably the oil pump, but he wanted to do a test to be sure -- also listened to his theory that the previous owner had had the light go off, waited until cold weather prevented the light from going off (colder oil = more oil pressure), and sold the car. Researched whether or not the dedicated VW seller in town would do the work for less. Told the original mechanic to go ahead with the test -- as the dealership would be at least $130 more. Found out yesterday that the oil pressure was fine: a tiny little spring in the oil pressure sensor had Gone Bad.
I had to laugh. Here's the previous owner: "Hey…I'll dick someone else over…they'll have to get a $700-dollar repair job…and I won't have to disclose it, so the dealership won't give me less money on it as a trade-in…no one will ever know..."
And it was just a spring. Just a little spring.