Quote:

Synthetics may result in leakage and lazy sure-grip operation.



Depends on what type/brand.


Quote:

Auburn does not recommend synthetics for new units either.



Auburn is making their “no synthetic” recommendation on information that’s over a decade old. A lot has changed in the lubricants industry in that time.

Similarly, up until 2003, Harley-Davidson recommended against the use of synthetic motor oil in their motorcycles. Then they came out with their Harley Davidson branded SYN3 synthetic motorcycle oil. (see also)

I don’t doubt that if Auburn reevaluated the current state of synthetic lubricants and the technology therein, they’d reconsider their recommendation.