Viscosity
Viscosities can be related horizontally only.
The viscosity/temperature relationships are based on 95 VI oils and are usable only for straight grade engine oils, gear oils, or other 95 VI oils.
Crankcase oils and gear oils are based on 100C viscosity. The "W" grades are classified on low temperature properties but must have minimum viscosities as shown above.
ISO oils and AGMA grades are based on 40C viscosity.