Motor Oil - Cold Cranking Cold Pumping

[Akro101]

I am confused. In reviewing the SAE J300 Table, I note that for 10W the maximum viscosity for cold cranking is 7,000 cP measured at -25C and the maximum viscosity for cold pumping is 60,000 cP measured at -30C.

I know that these measurements are done using different test apparatus and procedures, but if the viscosity units are the same (cP), how can an oil at the maximums allowed by the spec have a viscosity of 7,000 cP at -25C and a viscocity of 60,000 cP at -30C?

I understand that most oils would not actually be right at the max for both tests, I just don't understand the large diffence in the maximum numbers when they are measured only 5 degrees apart.

Thanks for any help you could give me.

 

[modistran]

the motor bible-which you can purchace on-line contains a wealth of info on viscosities and fossell v/s synthetic lube

 

[amorrison]

Standard Engineering Fluid Mechanics textbook charts here.

http://images.google.ca/imgres?imgu...rev=/images?q=+viscosity+chart&hl=en&lr=&sa=G

http://images.google.ca/imgres?imgu...rev=/images?q=+viscosity+chart&hl=en&lr=&sa=G