The dry boiling point, wet boiling point and -40C kinematic viscosity are the key points.

In GENERAL (not every single detail):

FMVSS DOT 3 = SAE J 1703 and ISO 4925 Class 3

FMVSS DOT 4 = SAE J 1704 and ISO 4925 Class 4 (but FMVSS allows a slightly highe... Login to read more.