Little different situation - that is a 8 forward and 2 reverse gear box plus the hydraulic fluids for the hydraulic pump(s).....
I would imagine that hot bacon grease would lube the gears
.....
however in a HST situation the game changes....... much like the transmission fluids we use to add to our ol Ford's, Chevy's and Dodge trucks back 30 years ago - you needed to use the correct one or bad things could/would happen.
The stress on the oils in a gear box are inherently different than those in a hydrostatic pump used for the transmission.