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Undisturbed penetration -- the method of determining the grease penetration without the grease being mixed or worked prior to the test. Indication of the penetration of the grease after sitting in the tube or pail for an extended time.

Unloading -- the release of contaminant that was initially captured by the filter medium.

Vacuum separator -- a separator that utilizes subatmospheric pressure to remove certain gases and liquids from another liquid because of their difference in vapor pressure.

Valve, by-pass -- a valve whose primary function is to provide an alternate flow path.

Valve, directional control -- a valve whose primary function is to direct or prevent flow through selected passages.

Valve, directional control, servo -- a directional control valve which modulates flow or pressure as a function of its input signal.

Valve, flow control -- a valve whose primary function is to control flow rate.

Valve, pressure control, relief -- a pressure control valve whose primary function is to limit system pressure.

Valve, relief, differential pressure -- a valve whose primary function is to limit differential pressure.

Valve -- a device which controls fluid flow direction, pressure, or flow rate.

Valve lifter -- sometimes called a "cam follower," a component in engine designs that use a linkage system between a cam and the valve it operates. The lifter typically translates the rotational motion of the cam to a reciprocating linear motion in the linkage system.

Vampire pump -- suction pump system used for sterile onsite component oil sampling available from The Fluid Life Corporation.

Vanadium (V) -- element number 23 on the periodic table of the elements. In the context of oil analysis vanadium can be present as a wear metal in various sampled components and the origins can be from such sources as: bunker oil, turbine blades and valves just to name a few.

Vapor pressure -- pressure of a confined vapor in equilibrium with its liquid at specified temperature thus, a measure of a liquid's volatility.

Vapor Pressure-Reid (RVP) -- measure of the pressure of vapor accumulated above a sample of gasoline or other volatile fuel in a standard bomb at 100°F (37.8°C). Used to predict the vapor locking tendencies of the fuel in a vehicle's fuel system. Controlled by law in some areas to limit air pollution from hydrocarbon evaporation while dispensing.

Varnish -- when applied to lubrication, a thin, insoluble, nonwipeable film deposit occurring on interior parts, resulting from the oxidation and polymerization of fuels and lubricants. Can cause sticking and malfunction of close-clearance moving parts. Similar to, but softer, than lacquer.

Viscometer or Viscosimeter -- an apparatus for determining the viscosity of a fluid.

Viscosity -- measurement of a fluid's resistance to flow. The common metric unit of absolute viscosity is the poise, which is defined as the force in dynes required to move a surface one square centimeter in area past a parallel surface at a speed of one centimeter per second, with the surfaces separated by a fluid film one centimeter thick. In addition to kinematic viscosity, there are other methods for determining viscosity, including Saybolt Universal Viscosity (SUV), Saybolt Furol viscosity, Engier viscosity, and Redwood viscosity. Since viscosity varies in inversely with temperature, its value is meaningless until the temperature at which it is determined is reported.

Viscosity, absolute -- the ration of the shearing stress to the shear rate of a fluid. It is usually expressed in centipoise.

Viscosity, kinematic -- the absolute viscosity divided by the density of the fluid. It is usually expressed in centistokes.

Viscosity, SUS -- Saybolt Universal Seconds (SUS), which is the time in seconds for 60 milliliters of oil to flow through a standard orifice at a given temperature.

Viscosity grade -- any of a number of systems which 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 commonly used measure of a fluid's change of viscosity with temperature. The higher the viscosity index, the smaller the relative change in viscosity with temperature.

Viscosity index improvers -- additives that increase the viscosity of the fluid throughout its useful temperature range. Such additives are polymers that possess thickening power as a result of their high molecular weight and are necessary for formulation of multi-grade engine oils.

Viscosity modifier -- lubricant additive, usually a high molecular weight polymer, that reduces the tendency of an oil's viscosity to change with temperature.

Viscous -- possessing viscosity. Frequently used to imply high viscosity.

Volatility -- this property describes the degree and rate at which a liquid will vaporize under given conditions of temperature and pressure. When liquid stability changes, this property is often reduced in value.

Wear -- the attrition or rubbing away of the surface of a material as a result of mechanical action.

Wicking -- the vertical absorption of a liquid into a porous material by capillary forces.

WinRoast® -- complete fluid analysis management software designed exclusively by the Fluid Life Corporation.

Worked penetration -- the method of determining the grease penetration after the grease has been mixed or worked. The grease worker (ASTM D217) is a perforated plate, which is pulled back and forth through a grease sample for 60 full strokes. The NLGI Grades are determined by the worked penetration. The grease may be worked for longer periods (i.e. 10,000 or 100,000 strokes) to evaluate the shear stability of the grease under extended service.

Yield point -- the minimum force required to produce flow of a plastic material.

ZDDP -- an antiwear additive found in many types of hydraulic and lubricating fluids. Zinc dialkyldithiophosphate.

Zinc (Zn) -- element number 30 on the periodic table of the elements. In the context of oil analysis zinc can be present as a wear metal in various sampled components and the origins can be from such sources as: brass, cathodic protectors, galvanizing, grease and oil additives just to name a few.