I have been refurbishing an old Thorens TD165 and decided to stick with Singer "sewing machine" oil as a safe bet (not their cheaper all purpose machine oil). Some of the synthetic oils contain Teflon and/or other materials, which has been said can break down and change into an abrasive with time (this is just heresay from the web, mind you). They sometimes contain other preservatives, which might be iffy depending on what material(s) the oil comes comes into contact with, like the TT belt and spindles. As far as I know the Singer oil has no negatives as long as you are not using it in a "grease" bearing and in this case it is not thick enough. Better yet is to use whatever oil the manufacturer recommends for your bearing as it was designed with this particular oil (and the weight of it) in mind, I would hope. I am not saying that all synthetic oils are bad, just that caution is advised in selecting the right one (don't just use anything).
