I used about 1 litre or so when I flushed out mine. I removed the side cover/ pto and sprayed all around inside using a parts sprayer. With the drain plug removed and catch pan under to catch flush fluid I was able to analyze the fluid for fillings and debris.
With the pto reinstalled I then refilled through the top using about .5 litre more then the recommended amount to a account for the pto the level is about 1/2 inch below the filler plug.
FYI I would not use in your kerosene heater with out running through a filter first it was pretty nasty!
