My 6 ton (I think) floor jack needs a top off of the jack oil. I didn't save the instructions and I have never had to refill or top one off before. How do you do one of these? Do you fill through the lowering screw or is there another fill port? Do you do it with the jack up or down?

I can't recall if the jack needs to be up or down, but usually there is a rubber fill plug on the side. It prys off, fill it there.

The jack would need to be down............otherwise you are building up pressure.......logically it makes sense.