Ditto on the jack oil, or power steering fluid should be about the right weight, also.
One bit of trivia, from my father, who was running a shop back in the days the knee action was being used, and repaired- - - -rebuilders at the time used to replace the factory needle bearings with bronze bushings when the units were reconditioned, and they had a habit of getting extremely stiff with the bushings installed. If your knee action units are not working smoothly, it's possible you've got rebuilt units with the wrong type of bearings in them.
Jerry
