Originally Posted by Gresp15C

Whether single or multi speed, a freewheel contains moving parts, including bearings and the ratchet mechanism which is usually pawls and springs. Any time you have moving metal parts, they need to be lubricated. How often they need to be re-lubricated depends on a lot of things, including how well sealed they are, and sources of contamination ranging from dust to road salt. It's pretty rare to re-lube a freewheel, partly because the moving parts are only moving when you're coasting. And the time honored lubrication technique is to let some light oil drip through the hub from one side to the other. I've done that on an old freewheel on a friend's "campus bike" that she gave to my daughter.

Originally Posted by Gresp15C

Whatever oil drips out would certainly "lube" the belt on a belt drive bike, and so hopefully the rubber is compatible with oil. (This is typical for any rubber used for automotive purposes). But it would be worth keeping an eye on, to make sure the belt isn't getting filthy.