Viscosity Index Formula:
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Definition: Viscosity Index is a measure of how much a fluid's viscosity changes with temperature.
Purpose: It helps determine the temperature-viscosity behavior of lubricating oils and other fluids.
The calculator uses the formula:
Where:
Explanation: The formula compares the viscosity change of the test oil to that of two reference oils.
Details: Higher VI indicates less viscosity change with temperature. Oils with high VI are preferred for applications with wide temperature ranges.
Tips: Enter the viscosities of aromatic oil, lube oil, and paraffinic oil in centistokes. All values must be > 0.
Q1: What is a good viscosity index value?
A: Most mineral oils have VI between 90-100. Synthetic oils can have VI > 100.
Q2: Why do we compare to aromatic and paraffinic oils?
A: These represent extremes - aromatic oils have low VI while paraffinic oils have high VI.
Q3: What units are used for viscosity measurements?
A: The calculator uses centistokes (cSt), the standard unit for kinematic viscosity.
Q4: How does temperature affect viscosity index?
A: VI itself measures how viscosity changes with temperature - higher VI means less change.
Q5: Can VI be greater than 100?
A: Yes, for some synthetic oils and highly refined mineral oils, VI can exceed 100.