What do these numbers mean?

[Smitty]

I see on product data sheets a segment that says cSt@40c and cSt@100c. What is the meaning of these numbers? Should I look for low or high numbers?

 

[Al]

These numbers represent kinematic viscosity at respective temperatures. The higher the number the higher the viscosity (thicker). 30 wt oils will give the upper number somwhere between 9.3 and 12.5 centistokes. Oils on the higher end of this number-say 11 would be thicker than mobil 1which is about 10 . This number represents the "thickness" at operating temperatures. And some would argue that thicker is better as far as wear is concerned.

 

[68redlines73]

This may be helpful to you as well.