Cold cranking viscosity VS actual viscosity?

[Ferrari]

What is the difference between the Cold Cranking apparent viscosity and the actual viscosity at the same temperature?

For example:

GC 0W-30
CC Viscosity @ -30C: 3200 cP
Viscosity @ -30C: 6767 cSt

Amsoil 0W-30
CC Viscosity @ -30C: 2993 cP
Viscosity @ -30C: 3821 cSt

The actual viscosity is close to double for the GC, yet the Cold Cranking viscosities are similar. Why is that?

 

[Dr. T]

Ferrari, where are these numbers from? Sources?

 

[Ferrari]

The CC viscosity #s were from Castrol and Amsoil respectively. The viscosity at -30C was calculated using the viscosity calculator here.

 

[JonS]

Maybe one is "slipperier" than the other. Even though it is thicker, it flows better???

 

[Ken2]

The cold cranking viscosity is the result of an actual test. Don't rely too much on a calculation.


Ken

 

[Chris A]

The calculated Vis is Kinematic
(mm2/s) @ temp °C, while the other is Cranking (mPa.s)max at temp °C.

I guess my question would be how are the two related, if at all?