MS-20 is selectively treated oil.
GOST 21743-76
It is applied in airplane piston engines. The oil is used as a part of oil mixtures in lubricating systems of turboprop engines.
MS-20 is applied in the axial bearing of helicopter propeller hubs. The oil is used in lubrication of gas pumping aggregations motocompressors. MS-20 is also applied in engine rotational speed regulators for diesel engines with autonomous oil systems and casings.