[C320-list] Gear Lube Oil?

[Martin Bayly]

Want to change the Gear Lube oil on my Yanmar 3YM30 diesel.

Bit new to this.  I understand the designations for the engine oil (10W-30
or 15W-40), but for the gear oil, the service manual refers to SAE Viscosity
#20 or #30 which according to the diagrams in the manual is somewhere in
between.  But don't see that kind of oil in the local stores.

 

So what do people use for the gear oil?  The same oil as the engine, or does
the marine gear need a special kind of oil - someone told me it needs
automatic transmission fluid - but not sure I buy that one?

 

Cheers

Martin