How about oil leaking from the oil pressure gauge everywhere behind the instrument panel, being ignored for too long, and getting sucked into the system at the (leaky) ignition switch vacuum lines? I think this is what happened on my car. I have oil in my climate control lines too, but my IP shutoff works and holds vacuum. My vacuum pump pulls a 20 or so. What a mess. I still have to find a way to get all that oil out of the lines.