Originally Posted By: eljefino
Maybe thru a funnel into the relief screw hole?
That would be the way. Try to clean the area around the fill hole before removing the plug.
It should be fairly easy to find where to refill it. Usually, it will be a fairly large screw in a location with no other obvious purpose. If you still have the owners manual, it probably shows the location.
Use Hydraulic Jack oil found at any automotive parts store such as CarQuest, NAPA, Advance. etc. It is very cheap (less than $2 for a bottle that can refill two nearly empty jacks).
Sure beats buying a new jack. I wonder how many people have thrown out perfectly good jacks that just needed a bit of oil.