20W non detergent motor oil vs Iso 46 or 68

[Tony H]

I got a small Walk behind mower with Hydro transmission. It calls for 20w or 20-50 wt non detergent motor oil. My thought was to use ISO 46 or 68 since the ISO is a real 20w hydraulic fluid and 20W non detergent is not sitting on anyones shelves.
Question:
Will this be OK?
Will the two fluids play nice together if I do not totally flush the system of the Motor oil? I was going to just turkey baster out the Reservoir and add the ISO.
The "Technician" at the Mower Manufacturer had no idea what ISO46 was sooooo, no help there.

 

[ruffdog]

The ISO 46 is about a 15/20 sae weight oil and the 68 is a 20w oil (both charts don't line up perfectly). The question would be if the ISO oil is going to lube any gears in the transmission enough.

https://www.tractorbynet.com/forums/oil-fuel-lubricants/293360-mix-hydraulic-fluids.html

 

[Tony H]

The ISO 46 is about a 15/20 sae weight oil and the 68 is a 20w oil (both charts don't line up perfectly). The question would be if the ISO oil is going to lube any gears in the transmission enough.

https://www.tractorbynet.com/forums/oil-fuel-lubricants/293360-mix-hydraulic-fluids.html

Thanks for that link..I understand a bit better. Hydro fluid was designed basically to turn a pump where my scenario has a gearbox involved. May not be enough Lubrication for gears. Hmm, I have a Cub Cadet where the Pump and rear axle is the same lube... I wonder if that would fly. I really need to find what they call for and forget the whole deal before I hurt something. I wish all these tractor manufacturers did not make it all such a mystery when in reality there may be only very few different fluids..