recommended oil for well tempered spindle cup

have classic well tempered TT and arm from the 90's, upgraded to black arm and platter.
can someone give some insight for the contradiction i read in several forums:

"The type of oil can be specific to a turntable design, but in general, motor oil is not a good choice.

Motor oil is usually multigrade and contains all sorts of additives. This bad. Light multi=purpose or sewing machine oil is a bit to thin. I use a monograde oil sold for air compressors at about SAE 20 or 30. Quite cheap. Synthetic is better than mineral oil if you can find some. I am just using mineral oil as sold at Tradetools for about $10 a litre bottle."

on the other hand:
“...any synthetic motor oil of any brand within a viscosity range of 5W-50 is acceptable.”
and this:
"For the spindle, he said Mr. Firebaugh, the designer, has updated the fluid to be synthetic motor oil, 5w20 or 5w30, whichever is cheaper. he said viscosity is not that important."