Study shows that PAO based synthetic oils have better viscosity index compare to Group – i, group – ii or group – iii oils (Without addition of any index significantly better than PAO-based lubricants of the same viscosity grade.

PAG based synthetic oil (Polyalkylene Glycol).

PAO Based synthetic Oil (Polyalphaolefin).

Normally when we are talking about the synthetic oils, then there are normally two types of synthetic oil available for widely used in different critical & high temperature applications. The viscosity index of synthetic oils ranges from 80 to over 400. VI-improving additives and high-quality base oils are widely used nowadays, allowing VI to be achieved over a value of 100. Since the scale’s inception, better oils have also been produced, making VI over 100 (see below). The scale was initially interpolated between 0 for naphthenic Texas Gulf crude and 100 for paraffinic Pennsylvania crude. The arbitrarily chosen temperatures for reference are 100 and 210 ☏ (38 and 99 ☌). The VI scale was established by the Society of Automotive Engineers (SAE).

(of a synthetic rubber), polyvinyl palmitate, polyvinyl caprylate, copolymers of vinyl palmitate with vinyl acetate, and various other materials used as viscosity index modifiers in a variety of petroleum oils.īelow is the table of viscosity indexes of different petroleum products & fluids for ref: Widely used materials are, for example, olefin copolymers (OCP), polyalkyl methacrylates (PAMA), poly isobutylene (PIB), styrene block polymers, methylmethacrylate (MMA), polybutadiene rubber (PBR), cis-polyisoprene. VI modifiers are normally used in multi-grade engine oils, gear oils and automatic transmission fluids, power steering fluids, hydraulic fluids and greases. This method is considered obsolete by ASTM and replaced by ASTM D2270. This is the method that determines the viscosity index of lubricating oils. Viscosity index means that it measures the change in viscosity with temperature – a high viscosity index indicates a small viscosity change of a petroleum product with changes in temperature.

The viscosity of oil usually decreases as the temperature increases. For user reference, 1 mm 2/s = 10 -6m 2/s = 1 cSt.ĪSTM D567 Method for Calculation of Viscosity Index from Viscosity at 100✯ and 210✯. The values stated in SI units are to be regarded as the standard.

No other units are there for measurement in this standard. Values stated in SI units are considered standard.Equations are already provided for calculation of viscosity index for products like petroleum with kinematic viscosity above 70mm2/s at 100 ☌. This practice applies to that petroleum or lubricating products whose kinetic viscosity is between 2mm 2/s and 70 mm 2/s at 100☌. The standard does not apply to petroleum products with a kinematic viscosity less than 2.0 mm2/s at 100 ☌.The standard covers procedures for calculating the viscosity index of petroleum products, such as lubricating oils, and related materials by their kinetic viscosities at 40☌ and 100☌.The viscosity index describes this change – a high viscosity index indicates a slight viscosity change with increase in temperature compared to a low viscosity index. If this reduction is significant, the system may not be sufficiently lubricated over the entire operating temperature range. Oil viscosity (see ASTM D445) usually decreases with increasing temperature. Below you will find a simple VI calculator. Normally, all things being equal, highly refined mineral oils with few contaminants have high VIs and Synthetic oils generally have a higher VI than mineral oils. Standard ASTM D2270 Calculates Viscosity Index by Measuring the Kinetic Viscosity of Liquids at 40° and 100☌ and ASTM D567 Method for Calculating Viscosity Index from Viscosity at 100✯ and 210✯. In turn, this means consistent, high performance in the machine. The best oils with the highest VI are stable and do not vary greatly in viscosity over a wide temperature range. Viscosity Index was measured by a scale of 0 to 100 however, modern science of lubrication has led to the development of oils with very high VI. High-VI liquids, in contrast, are less affected by temperature changes. Thus, a fluid with a low viscosity index will experience a relatively large swing in viscosity as temperature changes. The higher the VI, the smaller the change in fluid viscosity for a given change in temperature and vice versa. We can say that the it is the dimensionless number that shows how the temperature change can affect viscosity of an oil (engine oil and automatic gear oils, and power-steering fluids). The viscosity index (VI) is an arbitrary, unitless measure of a fluid’s viscosity change relative to a temperature change.

Kinematic viscosity of engine oil