ASTM D2270 Viscosity Index Calculation

ASTM D2270 is the practice for calculating viscosity index from kinematic viscosity at 40 °C and 100 °C. It is not a bench test of its own. The laboratory still measures those two viscosities — typically with ASTM D445 — and then applies the D2270 calculation to report a unitless index.

Lubricant producers and in-service oil programs use viscosity index to describe how much an oil thins as it heats. A higher index means less viscosity change between the two reference temperatures. The practice does not apply to products whose kinematic viscosity at 100 °C is below the range the calculation covers.

This page is original prose and is not a reproduction of the standard. Buy the official text from the ASTM store.

ASTM Standard at a Glance

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Recommended equipment for the D445 measurements behind ASTM D2270:

Choosing the right equipment for ASTM D2270

A viscosity index is only as good as the two kinematic viscosity values behind it. Laboratories that report D2270 need a viscometer that holds temperature and timing tightly at both 40 °C and 100 °C.

VeroVis is the Vero Scientific instrument for those D445 runs. Use it when you need the viscosities; use D2270 when you need the index calculated from them.