Quote:
Originally Posted by IamFODI
W ratings are based on pumpability – so, medium-to-high shear rates – at much colder temps than 40º C.
The viscosity measurements you got are of kinematic viscosity, which is a low-shear condition (basically how quickly gravity pulls it through a hole of a given size).
Kinematic viscosity at 40º C doesn't figure into SAE viscosity grades.
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Got ya, I was beginning to wonder that.
So the best we can do is compare this lukewarm 40C kin viscosity figure to the manufacturers figure? (where tested).
It seems that OA doesn't test the cold pumpabilty property? (At least mine and the previous one didn't). Is that typical for OA?
So my oil has sheared down thinner at 100C (as expected) to somewhere around 50 grade, and has also got thinner at 40C. The latter was not something I was expecting, my understanding is that as multigrade oil wears/shears down that the grade range shrinks, so it gets thinner at the hot end and thicker at the cold end. Is it because 40C simply isn't cold enough to show that? Or am I missing something?