Beaver 24" Scroll Saw (Model #3100)

I've just saved an old scroll saw from a trip to the junkyard, have stripped off several layers of paint and given it space in the corner of my workshop.
The base of this thing has a rather large reservoir to hold a lubricant. Inside is also a piece of felt that sits at the bottom.
What I'd like to know is:
What would be the preferred type of oil to use? Whether I should fill the entire cavity or merely keep the felt pad damp?
The following pictures are VERY similar to the model that I have:
*NB* The reservoir is behind the plate shown in closeup on the last pic.
Any advice would be greatly appreciated.
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