1. What is Viscosity Index?

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.

2. How Does the Calculator Work?

The calculator uses the formula:

Where:

• \( VI \) — Viscosity Index
• \( L \) — Aromatic's Viscosity (Centistokes)
• \( U \) — Lube Oil Viscosity (Centistokes)
• \( H \) — Paraffinic Viscosity (Centistokes)

Explanation: The formula compares the viscosity change of the test oil to that of two reference oils.

3. Importance of Viscosity Index

Details: Higher VI indicates less viscosity change with temperature. Oils with high VI are preferred for applications with wide temperature ranges.

4. Using the Calculator

Tips: Enter the viscosities of aromatic oil, lube oil, and paraffinic oil in centistokes. All values must be > 0.

5. Frequently Asked Questions (FAQ)

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.