Where VBN is the viscosity blending number of the blend and e is the transcendental number 2.71828, also known as Euler's number. Simply multiply the kinematic viscosity of the liquid at a particular temperature by its density at that same temperature. Once the viscosity blending number of a blend is obtained with equation (2), the viscosity of the blend can be determined by using the invert of equation (1):

Maples (2000), Petroleum Refinery Process Economics, 2nd Edition, Pennwell Books, ISBN 0-87814-779-9) In using the above blending equation, it is necessary that all viscosities are determined at the same temperature, for example, 100 oC. Where w is the weight fraction (i.e., % ÷ 100) of each component of the blend. The second step involves using this equation: 4.1 The viscosity index is a widely used and accepted measure of the variation in kinematic viscosity due to changes in the temperature of a petroleum product. Where v is the viscosity in centistokes and ln is the natural logarithm (Loge). In this video, I explained Viscosity Index- Procedure to Determine VI - Numerical of VI. H kinematic viscosity at 40C of an oil of 100 viscosity index having the same kinematic viscosity at 100C as the oil whose viscosity index is to be. This is becoming more of a problem as the demand for low-viscosity lubricants, designed for high-speed engines, increases. The first step involves calculation of the Viscosity Blending Index (VBI) of each component of the blend using the following equation (known as a Refutas equation): Calculating the viscosity blending index of a liquid consisting of two or more liquids having different viscosities is a two step procedure.

Calculate viscosity index