SM-4,5

SM-4.5 is an oil mixture for turboprop engines of AI-20 and AI-24 aircraft operating in difficult operating conditions associated with the features of their design - the presence of gearboxes, and requiring the use of more viscous oils (compared to turbojet engines).

The contact loads between the gear teeth in the gearbox are very high, and if the oil viscosity is less than the required one, the required oil film thickness will not be able to form, and progressive engine wear will begin.

SM-4.5 is obtained by mixing mineral oils MS-8p and MS-20 in a ratio of 75:25 by mass fraction, which makes it possible to increase the viscosity of the mixture in comparison with MS-8p to a level sufficient for use in a gas turbine engine and transmission of a turboprop traction screw. engine.