Hi Diamondude,
This topic has been visited numerous times on this forum, with one most important conclusion being agreed upon by all - that viscosity depends on the characteristics of the drive system - including everything that rotates (bearing, tolerance, platter mass, drive method, motor torque, etc.).
A word of warning about 3-in-One. Stay away from it. A friend tried some a few years ago. After 6 months, it formed a sticky varnish which he had to work at to clean off.
I think that once you understand the 3 major goals:
a) protect the bearing
b) provide mechanical stability (so the bearing doesn't rock)
c) musical performance
you'll be better equipped to arrive at conclusions that work best for you.
It is this latter point (musical performance - percieve as nuance and microdynamics) that people overlook. While I specify extremely low viscosity for my bearings, your mileage may vary depending on your bearing implementation.
Rather than cover old ground, check here if this topic intrigues you: http://www.galibierdesign.com/prd_bearing.html
It's fairly easy to separate what's relevant to Galibier, vs. general principles applicable to turntables in general.
Cheers,
Thom @ Galibier