It really depends on the machine. I think some of the vintage motors took grease. Singer made a lubricant for motors and gears, however the have changed the formula for their lubricant. If you have the old Singer lubricant in the metal tube, you can use it for motors. There is a great deal of debate about if Vaseline Petroleum Jelly is okay to use in motors. Someone says that they have used PJ for 35 years with no ill effect. Those selling the new Sew-Retro or Nova's Motor Lubricant claim that it is like the old Singer and is safer for those motors that take lubricant.
Someone recently posted this about lithium grease - "It is a very good grease when it is fresh, but it sadly hardens after some time, especially in a machine that doesn't see frequent use. "
I have heard that there are some who have had to chip the hardened grease off vintage machines. Tri-Flow grease or the new Singer lubricant would be fine to work on the gears for vintage machines. On the newer machines, follow the manufacturer's recommendation for lubricant.
Janey - Neat people never make the exciting discoveries I do.
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