In article 3183eab.0309171833.24feba39
@posting.google.com, says...
I will stick my neck out and say that you don't need special hydraulic
oil in a jack. But I would not use chainbar oil or motor oil. What I
think you want is a low viscosity oil with some antirust additives.
So my choice would be ATF
( unless hydraulic jack oil is cheaper ).

I was about to make the same comments. The only downside to
ATF vs. hydraulic oil I can forsee would be the detergent
additives, but doubt that would be a big deal in a jack.

I would definitely avoid bar oil, way too heavy and
whatever is added for tackiness is a bad thing.

Ned Simmons