In article , mike wrote:
On 27-03-2021 17:01 Scott Dorsey wrote:

Viscosity breakdown with time,
viscosity curve with temperature, adhesion, solvent characteristics,
ability to keep particulates in solution, three-ball test, etc.

All oils "breakdown with time."

Yes, that's why you test it. It's been forty years since I took tribo class,
but at the time there was a standard measurement with a rotating drum inside
a stationary drum that creates high shear on the test sample. You measure
viscosity regularly and plot it against time.

Clean linear paraffin oils did well on the test, oils with a lot of
crosslinking or rings did poorly.

You'd think a "synthetic oil" base would be pure linear paraffin chains with a
very narrow range of molecular weights and you might be right or you might
be terribly wrong, depending. Also, of course, the VI breaks down, not just
the base oil.
--scott

--
"C'est un Nagra. C'est suisse, et tres, tres precis."