The Strongest Savage Diff Compilation.

[thzero]

It would seem that with a higher vicosity oil that it would resist being pushed aside, therefore maintain lubrication and a small layer between the gears better than a lighter oil. Thus it would reduce the amount of metal on metal contact. But then again I'm not a chemist either.

Originally Posted by JasonB

I could be wrong here, but the friction vs wear thing makes since to me because the higher friction caused by the thicker oil forces more metal on metal pressure between the gears resulting in a shorter lifespan.