The most important rheological parameter for lubricants is viscosity as it also affects the tribological properties like friction between interacting surfaces and wear. This research intends to study the relationship between viscosity and temperature at different shear rates for multiple grades of three different categories of lubricants used for different applications viz. L1: MG20W50 (engine oil), L2: SAE20W50 (engine oil), L3: MC20W50 (mineral engine oil), L4: EP90 (gear oil), and L5: DXTIII (steering fluid). Constant high dynamic viscosity, shear stress, and low compressibility at different temperatures in multigrade as well as single grade industrial oil will help to maintain the surface film over the period of time and hence the reduction in wear. The dynamic viscosity of these chosen samples has been measured experimentally in temperature range of 20 to 50°C. The measurements have been extended to observe the dependence of shear rate, time, and temperature on the dynamic viscosity. All the samples are observed to behave like Newtonian fluids in the entire temperature range of study. Further, all samples seem to obey the Arrhenius relationship with temperature. Shear stress shows linear variation with shear rate exhibiting uniform viscosity which is substantiated by almost no variation in dynamic viscosity with shear rate for value above 5 per second. 1. Introduction The role of lubrication is an important part in the field of tribology. Lubrication is to smoothen the movement of one surface over another and to maintain the viscoelastic behavior [1]. Lubricants are commonly used for lubrication to reduce the friction and wear of surfaces in contact [2] and effective heat transfer due to good thermal conductivity. Most lubricants are liquids (such as mineral oils, synthetic oil, silicon fluids, water, etc.). Selection of lubricant is very important for providing machine tools a longer life. To select an appropriate lubricant, it is necessary to know its properties, lubrication system of applied machinery, conditions of machinery, cost of lubricant [3]. Common properties of lubricating oil are: viscosity, viscosity index, density, compressibility, surface tension, cloud point, pour point or low temperature property, flash point, friction coefficient, high boiling point, low freezing point, thermal stability, corrosion prevention, high resistance to oxidation, and so forth. The most important property is its viscosity. Viscosity is a function of temperature and pressure. The relationship between the viscosity and temperature and the relationship
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