What Viscosity Index is
Viscosity Index (VI) is a number indicating how stable an oil's viscosity remains against temperature change. Mineral base oils typically have a VI around 90–100, while synthetic or semi-synthetic oils can reach a VI above 140.
Why a high VI isn't always ideal
In high-speed gearboxes with precise cooling systems, excessive viscosity stability against temperature can mean the oil is thinner than ideal for forming an adequate lubricating film at normal operating temperature. In these applications, precisely matching the VG grade to manufacturer specifications matters more than maximizing VI.
MAADANOL's approach to this trade-off
MAADANOL GEAR-EP's formulation balances VI and its EP additive package so that it provides both adequate thermal stability for outdoor applications and a maintained lubricating film at standard operating temperature; the technical team recommends a specific grade for specialized, high-speed gearboxes.
Key Takeaways
- A higher Viscosity Index means more temperature stability, not necessarily better performance
- High-speed gearboxes need a more precise balance between VI and film thickness
- For specialized gearboxes, review manufacturer specs with MAADANOL's technical team
