If a sphere is dropped into a fluid, the viscosity can be determined using the following formula: 2 g a 2 ( ) 9 v. Both cases are not desired because the oil no longer optimally fulfils the required lubricating properties for the application. Viscosity is measured in terms of a ratio of shearing stress to the velocity gradient in a fluid. The viscosity of the oil can either increase or decrease. Viscosity Index (VI) is one approach used widely in the lubricating field to assess the variation of viscosity with temperature. Based on the methodology, Pennsylvania crude (paraffinic) was set as a benchmark at one extreme, representing low viscosity changeability relative to temperature. It is an empirically derived, unitless number. If this happens the oil should be changed. The viscosity index was developed for this purpose (ASTM D2270) by E. If the viscosity of the oil deviates greatly from the initial values of the fresh oil, this is an indication that accelerated oil aging has occurred. Not only does oil change its viscosity due to temperature influences and pressure, but the environmental influences during operation can also have a lasting effect on the flow properties. In addition, the viscosity index of oils can be artificially increased by adding high-performance additives (VI improvers). In the meantime, the scale has reached values of up to 400, due in part to modern production processes for temperature-stable synthetic oils. The viscosity index started at 0 (very temperature-dependent oils) and went up to 100 (oils with low temperature dependence). When the viscosity index was developed in 1928, the scale was based on the mineral oil types known at the time. The calculator on this site is for informative purposes only and we make no claims as to the accuracy. Their lubricating properties become unstable at high or low temperatures. Calculate the viscosity using the viscosity index. The oils with a low viscosity index can be influenced more strongly by the temperature. The oil retains its lubricating properties in a wider temperature range. Oil with a high viscosity index is less temperature dependent. In order to measure viscosity at cold temperatures other than by using ASTM D-445, the ASTM D-2602 method with. To a certain extent, the viscosity index is also an indication of the quality of an oil and serves the comparability of different oil types. If the viscosity of the oil used exceeds the required viscosity, it may cause damage due to excess operation, but if the viscosity is too low, the oil cannot form the required oil film, and scratching or other such problems may occur.

The viscosity behaviour at 40 вЊ and 100 вЊ is measured. It refers to the kinematic viscosity of an oil. The viscosity index (VI) is the behaviour of the lubricant as a function of temperature. A viscosity index improver is a complex polymer additive that expands at elevated temperatures to thicken the lubricant and ensure a more stable and consistent.

Viscosity index