Cold Cranking Cold Pumping Viscosity
Cold Cranking Cold Pumping Viscosity
(OP)
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 difference in the maximum numbers when they are measured only 5 degrees apart.
Thanks for any help you could give me.
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 difference in the maximum numbers when they are measured only 5 degrees apart.
Thanks for any help you could give me.





RE: Cold Cranking Cold Pumping Viscosity
It sounds to me like the MRV is more of a bulk viscosity, while the CCS is more thin-film- sort of like kinematic- versus high temperature high shear testing. Also, I gather that the real key parameter in the MRV is the absence of yield stress, and the measured viscosity isn't usually the killer. So a passing oil could have a vis considerably below the 60K max while just squeaking under the CCS limit.