Sean,
I think that you missed the point about viscous damping. The intent is to compensate for stylus drag. The drag from a stylus is highly variable exerting a very small but non-uniform braking force. The theory behind viscous damping is that applying a highly uniform braking force that is many times greater than stlyus drag will swamp out the effect of the stylus. I can't prove the validity of this theory, but there seems to be a great deal of supporting evidence. The primary evidence is that the vast majority of high-end turntables have bearings with a lot of vicous damping and are decidedly not optimized for low friction.
Variance in viscosity is not an issue for two reasons. 1) Temperatures in a turntable bearing will not change enough to be meaningful. There simply is not enough energy present to affect more than a one or possibly two degree temperature change. 2) The magnitude of drag is relatively unimportant. Any change in drag from temperature will be slow and gradual enough to be irrelevant.
Back to the original thread, my experience is that bearing oil viscosity does make a small difference in sound. My unproven theory is that oil with the higest viscosity that produces laminar (non-turbulent) flow in the bearing will be optimal. Turbulent flow will produce less uniform drag. So the objective is to maximize drag without turbulence. Radial bearing clearance and bearing design both effect flow so the best viscosity will be different for each bearing design.
Beyond viscosity it is difficult to imagine that additives or expensive formulations would be relevant. When it comes to lubrication a turntable bearing is a cake walk. Low temp, low speed, low pressure and clean.
I think that you missed the point about viscous damping. The intent is to compensate for stylus drag. The drag from a stylus is highly variable exerting a very small but non-uniform braking force. The theory behind viscous damping is that applying a highly uniform braking force that is many times greater than stlyus drag will swamp out the effect of the stylus. I can't prove the validity of this theory, but there seems to be a great deal of supporting evidence. The primary evidence is that the vast majority of high-end turntables have bearings with a lot of vicous damping and are decidedly not optimized for low friction.
Variance in viscosity is not an issue for two reasons. 1) Temperatures in a turntable bearing will not change enough to be meaningful. There simply is not enough energy present to affect more than a one or possibly two degree temperature change. 2) The magnitude of drag is relatively unimportant. Any change in drag from temperature will be slow and gradual enough to be irrelevant.
Back to the original thread, my experience is that bearing oil viscosity does make a small difference in sound. My unproven theory is that oil with the higest viscosity that produces laminar (non-turbulent) flow in the bearing will be optimal. Turbulent flow will produce less uniform drag. So the objective is to maximize drag without turbulence. Radial bearing clearance and bearing design both effect flow so the best viscosity will be different for each bearing design.
Beyond viscosity it is difficult to imagine that additives or expensive formulations would be relevant. When it comes to lubrication a turntable bearing is a cake walk. Low temp, low speed, low pressure and clean.