Thanks! I know I'm grave digging but I just had to ask for a follow up, I did so publicly because I'm sure I'm not the only one who's curious. This topic was referenced in an article of about the same age on SPCR, and the lack of a conclusion was killing me.

I think I'll give this a try as an exhaust fan, and see how long it takes for the oil treatment to wear off and the vibration to return. I had turned off the test setup while I typed this up, and when I turned it back on just now the vibration was still gone. So, uh, Felger Carbon , how's that fan ...