[Fritz Peyerl]

How could you have any dampening action without any liquid in it. I still say it should be oil. How do you get water into it? you have a seal / O ring below the top nut and the shaft strut shaft moving up and down has a tight seal around.
If you study the open strut you will see a small piston ring on bottom end and a a check valve in the insert housing and a check valve on top of the moving part. The oil it self is the dampening fluid and also is used to transfer the heat to the outside.
Antifreeze has NO lubrication factor and can imagine how much friction there is when that little piston ring goes up and down to dampen your ride. It can't be anything else than oil. even if you should get a drop of water into it, it will not burst the housing or do any damage.
My original question was how much oil and what type. It looks like no body has a real answer.