Viscosities can be related horizontally only. For example, the following oils have similar viscosities: ISO 460, AGMA 7 and SAE GEAR OIL 140.
The Viscosity/temperature relationships are based on 95 VI oils and are usable only for mono grade engine oils, gear oils and other 95 VI oils.
Crankcase oils and gear oils are based on 100°C viscosity. The *W” grades are classified on low temperature properties. ISO oils and AGMA grades are based on 40°C viscosity