Viscosity Index Calculator

Formula

The formula to calculate the Viscosity Index (VI) is:

\[ VI = \frac{L - U}{L - H} \]

Where:

\( VI \) is the viscosity index
\( L \) is the kinematic viscosity of oil at 40°C of 0
\( U \) is the kinematic viscosity of lubricant
\( H \) is the kinematic viscosity of oil at 40°C of 100

Definitions

Viscosity Index (VI): A measure of the change in the viscosity of a lubricant with changes in temperature. A higher VI indicates a smaller change in viscosity with temperature.
Kinematic Viscosity of Oil at 40°C of 0 (L): The kinematic viscosity of a reference oil at 40°C with a viscosity index of 0.
Kinematic Viscosity of Lubricant (U): The kinematic viscosity of the lubricant being measured.
Kinematic Viscosity of Oil at 40°C of 100 (H): The kinematic viscosity of a reference oil at 40°C with a viscosity index of 100.

Example

Let's say the kinematic viscosity of oil at 40°C of 0 (L) is 100, the kinematic viscosity of the lubricant (U) is 80, and the kinematic viscosity of oil at 40°C of 100 (H) is 60. Using the formula:

\[ VI = \frac{100 - 80}{100 - 60} \]

We get:

\[ VI = 0.50 \]

So, the viscosity index is 0.50.