5 gal of bobcat hyd oil is $ 71.62 and you will take the risk of wrecking $5000.00 plus worth of parts to use an unknown oil? just doesn't make a lot of sense to meNot sure its really wise.
I assume its screw compressor oil. From what i remember putting into my compressor, it had some weird additives. I just don't know how it would react with the pump.
For the price of 15W40, its really not worth the risk.
You could probably flog the compressor oil off or even swap it for 15W40?