Filling Hydraulic Jack (Oil)?

[Dobber30052]

I have a Ssears 8 ton hydrulic jack that has served me well for many years and my dad (RIP) for many more years before that. Well, today I finally got 'round to replacing a busted beam in my tractor barn (don't worry the tractor has been out of danger!). After rigging a jack system, a seal or something blew on the jack. I took it apart, saw nothing irregular, cleaned it and put it back together. Then I tried to figure out how much oil to put in it. There are 2 plugs, one at the bottom, and one about midway up the cylinder. My inclination is that the mid plug is the fill line, much like an outboard or my Farmall B. At this point, I have filled it to the mid point plug. It seems to work OK. What do think (or hopefully, know) about this?

Thanks for all of the great posts!

Dob