first oil change, now weird noises...

[paanta at splatterfish.com]

All,
  I finally got around to replacing the oil on my "new" 140K mile old
5ktq.  Last oil change was one owner back, so I was anxious to get it
done.
  I switched from castrol synth/dino blend to Mobil 1 15w50.  At least,
I'm told it was the castrol blend.
  Not knowing _exactly_ how much oil the car takes, I put in ~4.9
quarts.  This overfilled it maybe 1/8"-1/4" over the max fill line.
  Since changing the oil, I get a squeal/howl/scary noise from the car.
It starts howling about one to two minutes after startup and goes
away after maybe 15 minutes when the car is good and hot.  It
makes the noise at idle, and its slightly worse as engine speed
increases.  I think the best way to describe it is the sound you get
from rubbing your finger around the rim of a crystal wine glass, but
much lower pitched and more intermittent.
  Question is...is it angry because I switched to mobil 1 15w50 (too
thick??), or is it angry because I overfilled it slightly?  WTF is this
noise?  Is it permanent??  The car runs otherwise just fine.

  -Pat