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The higher the VI, the more stable the viscosity remains over some temperature range. The VI was originally measured on a scale from 0 to 100; however, advancements in lubrication science have led to the development of oils with much higher VIs. [1] The viscosity of a lubricant is closely related to its ability to reduce friction in solid body ...
Understanding the temperature dependence of viscosity is important for many applications, for instance engineering lubricants that perform well under varying temperature conditions (such as in a car engine), since the performance of a lubricant depends in part on its viscosity.
For kinematic viscosity, the SI unit is m^2/s. In engineering, the unit is usually Stoke or centiStoke, with 1 Stoke = 0.0001 m^2/s, and 1 centiStoke = 0.01 Stoke. For liquid, the dynamic viscosity is usually in the range of 0.001 to 1 Pascal-second, or 1 to 1000 centiPoise. The density is usually on the order of 1000 kg/m^3, i.e. that of water.
The activation energy Q takes a different value depending on whether the high or low temperature limit is being considered: it changes from a high value Q H at low temperatures (in the glassy state) to a low value Q L at high temperatures (in the liquid state). Common logarithm of viscosity against temperature for B 2 O 3, showing two regimes
The grades with a W designation are considered Winter-grades, and denote an engine oil's low-temperature properties, while non-winter grades denote an engine oil's properties at the operating temperature of an engine. [5] The SAE 8 through SAE 16 viscosity grades describe oils that can improve fuel economy through reduced hydrodynamic friction ...
The clear cut definition of light and heavy crude varies because the classification is based more on practical grounds than theoretical. The New York Mercantile Exchange (NYMEX) defines light crude oil for domestic U.S. oil as having an API gravity between 37° API (840 kg/m 3) and 42° API (816 kg/m 3), while it defines light crude oil for non-U.S. oil as being between 32° API (865 kg/m 3 ...
The viscosity of the sample is then calculated using the following equation: = ˙ where is the sample viscosity, and is the force applied to the sample to pull it apart. Much like the Meissner-type rheometer, the SER rheometer uses a set of two rollers to strain a sample at a given rate. [ 31 ]
DOT 5.1 fluids are specified with low viscosity over a wide range of temperatures, although not all cars fitted with ABS or ESP specify DOT 5.1 brake fluid. [12] For a faster reaction of the ABS and ESP systems, DOT 4 and DOT 5.1 brake fluids exist with low viscosity meeting the maximum 750 mm 2 /s viscosity at −40 °C (−40 °F) requirement ...