I did some research among the antique fan collectors on the web.
Here's what's been recommended, in no particular order:
1. SAE 20 *non-detergent* motor oil
2. Turbine oil (ISO 32 SAE 15)
3. 3-in-1 Electric Motor Oil (SAE 20) *note* Not the multipurpose "red
can" stuff, but the blue can motor oil.
4. Royal Purple Synthetic INDUSTRIAL oil ISO 68 ~ SAE 25
5. Lithium grease in an aerosol spray--what I use. Be sure to shake
the can before application.
FWIW,
Chuck