I only have a 250 (vintage, very simple) one, but I've looked up the 252 on the net, and I've found a few pictures of it, from which I can hardly fancy that there's an oil tank there.
But if you have one, why can't you take it apart and make sure how it works?
 

The Premier 252 pedal is a single post design with a "T" handle on the upper right to adjust tension.  If this is the pedal that you have, it is has a compression spring design similar to the Ludwig Speed King but with easier spring tension adjustment (from the top rather than from the underside).  This system utilizes a cam that compresses a spring on the down-stroke, rather than a lever that stretches a spring, as on most contemporary pedals (DW5000-9000, Tama Iron Cobra, Yamaha FP series, etc).  The cam action is just like the valve cams on an automobile engine and need lubrication to ensure smooth operation and to lessen the wear factor.  I suspect the 252 needs grease rather than oil, but I don't know how or where to add it.

BTW, the Tama King Beat pedal was an ...ummmm... adaptation of the 252.