Oils without the letter W, intended for use at higher temperatures, are based on the viscosity at 100oC only. This provides a measure of an oils’ ability to flow to the engine oil pump inlet and provide adequate engine oil pressure during the initial stages of operation. Borderline pumping temperature is measured according to ASTM D3829 ‘Standard Method for Predicting the Borderline PumpingBorderline Pumping Temperature of Engine Oil’. Viscosities measured by this method have been found to correlate with engine speeds developed during low temperature cranking. The low temperature viscosity is measured by means of a multi-temperature version of ASTM D2602 ‘Method of Test for apparent Viscosity of Motor Oils at Low temperature using the Cold Cranking Simulator’. Grades with the letter W are intended for use at lower temperatures and are based on a maximum low temperature viscosity and a maximum borderline pumping temperature, as well as a minimum viscosity at 100C. In this system two series of viscosity grades are defined – those containing the letter W and those without the letter W. The most widely used system for engine oil viscosity classification is that established by the Society of Automotive Engineers (SAE) in the USA. LUBRICANT VISCOSITY CLASSIFICATIONS / ENGINE OIL LUBRICANT CLASSIFICATIONS In this case the viscosity brackets for the higher viscosity grades are measured at 100 C. The AGMA Standard 251.02 details specifications for three types of open gear lubricants – rust and oxidation inhibited (R and O), extreme-pressure (EP) and residual type gear oils. Oils marked ‘comp’ are compounded with 3 to 10% fatty material. Viscosity Limits of Former AGMA Classifications SUS at 100☏Ĝorresponding ISO Viscosity Grade The viscosity brackets correspond to those given in ASTM D 2422 Standard Recommended Practice for Viscosity System for Industrial Fluid Lubricants.ĪGMA Viscosity Grades for Enclosed GearingĪGMA Lubricant No. AGMA Standard 250.04 details specifications for rust and oxidation inhibited (R and O) and extreme-pressure (EP) lubricants used in enclosed gear drives. The American Gear Manufacturers Association (AGMA) have issued specifications and recommendations for gear lubricants used in various types of gear application. NLGI Consistency (Grade No.)ĚSTM Worked Penetration at 25☌ NLGI Grease Classification (National Lubricating Grease Institute This system is used to classify industrial greases. The consistency, defined by the distance in tenths of a millimetre, that a standard cone penetrates a sample of the grease number under standard conditions at 25oC. The classification consists of a series of consistency range, each of which is defined by a number (or numbers) 000 to 6. This classifies greases solely in terms of their hardness or softness no other property or performance level is taken into consideration. The commonly used grease consistency classification is that established in the USA many years ago by the National Lubricating Grease Institute (NLG). ISO Viscosity Grade (ISO VG) Minimum Maximum Mid-Point Cutting oil and some other specialized products are more important in relation to grade selection. This system is now used to classify all industrial lubricating oils where viscosity is an important criterion in the selection of the oil. This is illustrated in the table below, which shows the ISO viscosity grade numbers, the mid-points of each bracket, and the viscosity limits For example, ISO viscosity grade 32 relates to the viscosity bracket 28.8 to 35.2 mm2/s, the mid point of which is 32.0 mm2/s. The numbers indicate to the nearest whole number, the mid points of their corresponding brackets. It consists of a series of 18 viscosity brackets between 1.98 mm2/s and 1650 mm2/s, each of which is defined by a number. The ISO viscosity classification uses mm2/s (cSt) units and relates to viscosity at 40oC. ISO (International Standards Organisation) viscosity classification. We explain the mechanics behind the different grade classifications of car / motorcycle oils & greases.
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