Properly refurbishing a compass entails a little more than merely “topping up the oil”.
Everything (jewel, pivot, card & dome) must be scrupulously clean, the dome uncrazed, the seals
still sealing, etc.
The Danforth Compass website doesn’t offer much information, except there is a service
centre locator: http://www.danforthcompass.com
Until recently, most compasses used Odorless Mineral Spirits as their damping fluid.
Ritchie (for one) now uses a fluid called Isopar L ® (*1) that has similar properties, but with some added benefits over Odorless Mineral Spirits. The two can be mixed together.
(*1) Isopar L® is a Registered Trademark of Exxon Mobil Corporation - generically known as: Isoparaffinic hydrocarbons (Isoparaffin), Hydroheated heavy naphtha (petroleum).
Some older style (up to 1960's) Compasses used an Isopropyl Alcohol and water
mix, or Kerosene.