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Poise (absolute viscosity) -- a measure of viscosity numerically equal to the force required to move a plane surface of one square centimeter per second when the surfaces are separated by a layer of fluid one centimeter in thickness. It is the ratio of the shearing stress to the shear rate of a fluid and is expressed in dyne seconds per square centimeter (DYNE SEC/CM2); 1 centipoise equals .01 poise. Polar compound -- a chemical compound whose molecules exhibit electrically positive characteristics at one extremity and negative characteristics at the other. Polar compounds are used as additives in many petroleum products. Polarity gives certain molecules a strong affinity for solid surfaces; as lubricant additives (oiliness agents), such molecules plate out to form a tenacious, friction-reducing film. Some polar molecules are oil-soluble at one end and water-soluble at the other end; in lubricants, they act as emulsifiers, helping to form stable oil-water emulsions. Such lubricants are said to have good metal-wetting properties. Polar compounds with a strong attraction for solid contaminants act as detergents in engine oils by keeping contaminants finely dispersed. Polishing (bore) -- excessive smoothing of the surface finish of the cylinder bore or cylinder liner in an engine to a mirror-like appearance, resulting in depreciation of ring sealing and oil consumption performance. Polyalphaolefin (PAO) -- the most widely used synthetic oil in lubricating oils exhibiting good low points, long oxidation life, and low volatility. Most similar to characteristics of mineral oils and commonly blended with mineral oil base stocks. Polyglycol -- polymers of ethylene or propylene oxides used as a synthetic oil base. Properties have very good hydrolytic stability, hydrocarbon insoluble, high viscosity index and low volatility. Polymerization -- the chemical combination of similar-type molecules to form larger molecules. Polyol ester -- synthetic oil with high temperature stability and low volatility. Used extensively in aviation jet engines. Pore -- a small channel or opening in a filter medium which allows passage of fluid. Pore size distribution -- the ratio of the number of effective holes of a given size to the total number of effective holes per unit area expressed as a percent and as a function of hole size. Porosity -- the ratio of pore volume to total volume of a filter medium expressed as a percent. Positive crankcase ventilation (PCV) -- system for removing blow-by gases from the crankcase and returning them through the carburetor intake manifold to the combustion chamber where the recirculated hydrocarbons are burned. A PC valve controls the flow of gases from the crankcase to reduce hydrocarbon emissions. Potassium (K) -- element number 19 on the periodic table of the elements. In the context of oil analysis potassium can be present as a contaminant in various sampled components and the origins can be from such sources as: coolant inhibitors, fuel elements, granite and road dust just to name a few. Pour point -- lowest temperature at which an oil or distillate fuel is observed to flow, when cooled under conditions prescribed by test method ASTM D 97. The pour point is 3°C (5°F) above the temperature at which the oil in a test vessel shows no movement when the container is held horizontally for five seconds. Pour point depressant -- an additive which retards the adverse effects of wax crystallization, and lowers the pour point. Power unit -- a combination of pump, pump drive, reservoir, controls and conditioning components which may be required for its application. PPM -- parts per million. Predictive maintenance -- a type of condition-based maintenance emphasizing early prediction of failure using non-destructive techniques such as vibration analysis, thermography, and wear debris analysis. Pressure -- force per unit area, usually expressed in pounds per square inch. Pressure, absolute -- the sum of atmospheric and gage pressures. Pressure, atmospheric -- pressure exerted by the atmosphere at any specific location. (Sea level pressure is approximately 101.33 Kilopascals or 14.7 pounds per square inch absolute.) Pressure, back -- the pressure encountered on the return side of a system. Pressure, cracking -- the pressure at which a pressure operated valve begins to pass fluid. Pressure, rated -- the qualified operating pressure which is recommended for a component or a system by the manufacturer. Pressure, system -- the pressure which overcomes the total resistances in a system. It includes all losses as well as useful work. Pressure drop -- Resistance to flow created by the element (media) in a filter. Defined as the difference in pressure upstream (inlet side of the filter) and downstream (outlet side of the filter). Pressure gage -- pressure differential above or below atmospheric pressure. Pressure line filter -- a filter located in a line conducting working fluid to a working device or devices. Preventive maintenance -- maintenance performed according to a fixed schedule involving the routine repair and replacement of machine parts and components. Proactive maintenance -- a type of condition-based maintenance emphasizing the routine detection and correction of root cause conditions that would otherwise lead to failure. Such root causes as high lubricant contaminant, alignment and balance are among the most critical. Propylene glycol -- also known as 1,2-propanediol, is an organic compound (a diol alcohol), usually a tasteless, odourless, and colourless clear oily liquid that is hygroscopic and miscible with water, acetone, and chloroform. It is manufactured by the hydration of propylene oxide. Propylene glycol can also be used as antifreeze. Propylene glycol is less toxic to humans than ethylene glycol. PSIA -- pounds per square inch absolute. (PSIG + 14.696) PSID -- pounds per square inch differential. PSIG -- pounds per square inch gauge (PSIA - 14.696) Pump -- a device which converts mechanical force and motion into hydraulic fluid power. Pumpability -- the low temperature, low shear stress-shear rate viscosity characteristics of an oil that permit satisfactory flow to and from the engine oil pump and subsequent lubrication of moving components. Pump, fixed displacement -- a pump in which the displacement per cycle cannot be varied. Pump, variable displacement -- a pump in which the displacement per cycle can be varied. Qualitative oil analysis -- determining "which" wear metals and contaminants are present in a sample. Quantitative oil analysis -- determining "how much" of a wear metal or contaminant is present in a sample. Quenching oil -- is oil used to cool metal parts during their manufacture, and is often preferred to water because the oil's slower heat transfer lessens the possibility of cracking or warping the metal. qVisc -- an autosampling kinematic viscometer designed by the Fluid Life Corporation.
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