Conversely, if it is too thin at the operating temperature, it will not be able to guarantee a sufficient lubricating film to protect it from wear. When a machine is started, the oil must not be to viscous because otherwise it will not reach the areas that need to be lubricated in time. At the same time, however, it is the most decisive key figure for describing an oil’s capability to build a separating lubricating film between two moving parts. Viscosity itself is not a characteristic of quality.Ī viscosity reading simply tells you how thick or thin an oil is. Whether thin or thick, the viscosity of a modern lubricant is accurately adjusted nowadays to suit its intended use. The viscosity of this paste was, however, altered in Roman times, for example with honey. “Viscous” therefore originally meant “sticky like birdlime”. Glue used to be extracted from the mistletoe for catching birds. The concept takes its name from the typically gooey sap that comes from mistletoe berries (viscum). Nearly all physical media and foodstuffs have a specific viscosity. Thin lubricating oils are mostly deemed to have low viscosity and thick lubricating oils are deemed to have high viscosity.īut viscosity isn’t just measured for lubricating oils or paints and adhesives. And the lower the viscosity, the thinner the oil. The higher the viscosity, the thicker the oil. Viscosity nowadays means a measurement of the flowability of a lubricating oil or hydraulic fluid. Several modern devices have been installed in the laboratory just for determining viscosity alone. OELCHECK principally assesses viscosity in oil samples at 40☌ and 100☌ and calculates the viscosity index from this. Since it can change when an oil is being used, it is one of the most fascinating and extensive topics in lubricant analytics. It is also dependent on temperature and can be infl uenced by special additives. It plays the decisive role in the choice of accompanying lubricant as it describes its fl uid characteristics. Viscosity is the most important physical characteristic of an oil. Learning more about your specific application can help deliver extra value and performance, while avoiding unnecessary expenses.The single most important physical characteristic of any oil We'd recommend looking also at oils by category (such as Spindle, Way, Gear, and Hydraulic oils) and consider between synthetic and conventional oils. Translating the viscosity is a good first step and can be sufficient for most general-purpose applications. This is a good approximation for most oils, but will lead to a small error when converting between ISO/AGMA and SAE for high Viscosity Index oils. The chart assumes the oil has a Viscosity Index of 95. Oil gets thinner according to its Viscosity Index, and the chart is calculated with a specific Viscosity Index (VI 95 default) ISO VG measures oil at 40✬ and a given range to +/-10% of their stated value, so ISO VG 100 oil will have a viscosity between 90 and 100 cSt at 40✬.ĪGMA has redefined its grades to align with ISO standards, so they line up exactly. Oils grades that are on the same horizontal line (with the correct Viscosity Index) on the chart are equivalent. Several organizations (ISO, SAE, AGMA) have created competing standards to define oil viscosity ranges, but most of them mean the same thing.
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