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Varnish – When applied to lubrication, a deposit resulting from oxidation and polymerization of fuels and lubricants. Similar to but softer than lacquer.
Viscometer – Viscosimeter – An apparatus for determining the viscosity of a fluid.
Viscosity – That property of a fluid or semi-solid substance characterized by resistance to flow and defined as the ratio of the shear stress to the rate of shear of a fluid element. The standard unit of viscosity in the c.g.s. system is the poise and is expressed in dyne sec. Per square centimeter. The standard unit of viscosity in the English system is the reyn and is expressed in lb. sec. Per square in. (1 reyn = 6.9 x 104 poise)
Viscosity Grade – Any of a number of systems that characterize lubricants according to viscosity for particular applications, such as industrial oils, gear oils, automotive engine oils, automotive gear oils, and aircraft piston engine oils.
Viscosity Index (VI) – A measure of a fluid’s change of viscosity with temperature. The higher the viscosity index the smaller the change in viscosity with temperature.
Viscosity Index Improver – Additive that increases lubricant viscosity index, necessary for formulation of multi-grade engine oils.