This International Standard establishes a system of viscosity classification for industrial liquid lubricants and related fluids. This includes mineral oils used as lubricants, hydraulic fluids, electrical oils and for other applications The usual method for kinematic-viscosity determination is that specified in ISO 3104, but this may give anomalous results when used with non-Newtonian fluids (i.e. those whose coefficient of viscosity varies significantly with rate of shear). For such fluids, it is therefore important to state the particular method by which viscosity has been de-termined.
It is also recognized that there may be some pure chemicals and naturally occurring products, used as lubricants, which will not fall within this classifi-cation.
BS 4231:1992 history
1992BS 4231:1992 Classification for viscosity grades of industrial liquid lubricants