SAE Engine Oil Divisions

Jay

Messages
1,607
Location
Idaho Falls, ID
I'm curious as to how the SAE came up with their grade divisions. Why aren't they nice even ranges? 20 weight covers a range of 3.7cSt. 30 weight 3.2cSt 40 weight 3.8cSt 50 weight 5.6cSt 60 weight 4.2cSt Anybody know how they come up with this?
 

MolaKule

Staff member
Messages
21,591
Location
Iowegia - USA
JAy, Partly historical and mostly mathematical, i.e., the way the mathematics yield the resultant numbers. When starting out to define viscosites, the main goal was not to have even numbers or numbers without decimal points, but to define a range of viscosities that met the International acceptance of the definition of dynamic and kinematic viscosities.
 
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