The oil collects dust and wear particles, all oil collects dust and wear particles. When applied to the common brass in mesh with steel the dust and wear particles are embedded in the softer material and serve as an abrasive to wear the harder material. Brass against steel tends to be self lubricating. That is why it is used.
The antique fiber gears are not supposed to be lubricated either, the oil attacks the resin and ruins them. And that is why Edison switched to a steel gear from fiber in the Opera. The winding gear and pawl is similar metal. The output gear may be similar or dissimilar depending on the manufacturer.
