IIRC, silicone oil is not meant for lubrication duties but for damping. But low cSt value silicone oil may behave like a thick lubricant.
Regarding single grade oil - based on recommendations from experienced users, I searched and searched for single grade, synthetic compressor oil which has no additives, but they're available only in industrial-sized quantities (20 liter and 200 liter) and not in retail quantities. I eventually found and bought compressor oil in a one liter can but I was not able to determine its grade, whether it is multi or single grade, whether it is synthetic or natural, whether additives are added or not added. I tried it for some time and it seems quite suitable for the purpose. Later I tried Mobil Delvac 10W30 diesel engine oil, doped with a small quantity of lithium grease. Even without the added grease, the Mobil Delvac is slightly thicker than the compressor oil. I still use it. If you search the net, you will find lots of different recommendations, and it can be quite confusing. I haven't found a definitive answer, so I ended up making my own (hopefully informed) conclusions. My reasoning for using the Mobil Delvac is that it is fully synthetic (I still don't know why it is superior to natural oil - may be better characteristics compared to natural ones??? but manufacturers sure don't forget to tomtom the fact that a particular oil is fully synthetic), has some additives to prevent gumming (some people maintain that additives are bad), recommended oil change interval is 100000 kms, and is designed for engines operating with much higher rpm than the typical TT bearing spindle, so it can't possibly be inadequate for our TTs that operate at much lower rpms than diesel car engines.
So far, on my own DIY-ed massive bearings carrying more than 8 kgs of stacked platters, the Mobil Delvac seems to be working very nicely. YMMV, of course.
All this is, of course, twisting ourselves our collective audio knickers into unnecessary knots. Just use Singer sewing machine oil and it will be more than adequate for most bearings. That different types of oils sound different is another matter, though.