nothing wrong with clock oils. as far as new engine oils, there are no corosives for brass or bronze. the old "non deturgent" "mineral oils" were replaced by synthetic motor oil. a great improvement ! i was working for standard oil when the "multi - viscosity" oil came out. many tests were were made. don't use it on watches. vin
There are references to FEF on the Incabloc website : http://www.incabloc.ch/en/pieces_rechanges.php
From Ranfft it looks like it should be the 6632 family on the first line.
The upper spring is the second last column : 975.03