After around two years of trial and error, I seem to have found a successful way of replacing the master fluid in Sata-Lites, so I thought I'd share.
This only works for bottles that are cloudy but still flow well. In my experience If the oil has gone sticky or separated, there's nothing that can be done.
The only things needed are distilled water, surfactant, and a very thin hose.
To start with, the bottle needs to be removed from the lamp and placed in a refrigerator for a couple of hours or so. Lowering the temperature of the oil tends to thicken it somewhat making it less likely to break up.
The next step is to remove the cap from the bottle, most simply unscrew. Beware though that some later types may have a plastic cap which is pressed on, this can usually be removed with a firm pull.
Once the bottle is open, the original master fluid can by syphoned out very carefully using the hose. Keep the end of the hose away from the oil, about an inch above it is best, to avoid sucking any up. Do not worry about leaving some of the original cloudy fluid inside the bottle. It will be diluted significantly later on and won't be noticeable.
Once the original fluid has been removed it's now time to refill the bottle with distilled water. Syphoning the water in very slowly is best, to avoid disturbing the oil. Fill the bottle up to the point where the neck just begins to narrow.
You're now ready to add the surfactant. I can't stress enough though how little of it you need compared to most lamps! Do not add it straight from the bottle, instead dip a pin or very fine needle into the surfactant and use this to transfer ONE DROP ONLY into the refilled bottle. Much more than this and the oil will stick to the glass bottle, and from unfortunate experience I've found it can never be salvaged.
You may now add a few drops of food colouring or water based ink to the bottle to colour the fluid if you like. Once that's done the only thing left to do is to replace the cap and you're done.
It may take a few hours for the lamp to begin to flow once refilled, and sometimes several cycles before it flows as it used to.
It's important to note that the flow in these Sata-Lites is always somewhat poorer than other lamps. They usually only produce round blobs that move slowly, occasionally bouncing off one another. The blobs will start off very large and reduce in size as the lamp warms up.
I do hope all (or at least some) of this is of help.