Our Hydraulic jacks had grease fittings but the manual said nothing of what to use in them.It said to spray and wipe down the rams while extended with silicone.
I use or rather where we stored it used about 20.00 a tube lithium grease that you can never get off your hands.I have some in the lawn equipment garage but hurt my knee and don't feel up to hobbling out there. The price doesn't matter, just get the best you can find in grease in oil and women. The last one chose me and she is still ticking just great and no oil or grease required.