Technical Need a little help...

I'm sure this has been addressed here before, but I must have missed it. And I can't seem to locate this info in my old Chilton's or Motor's manuals that cover those years. So here is the question. The fan hubs on the flathed Fords, (mine is a '51 F1) have a small screw to allow for adding lube to it. No one I've talked to has a solid answer on what weight oil or perhaps grease to use. Can anyone help? Thanks

 

this?

http://www.vanpeltsales.com/FH_web/flathead_oilfilledfan-servicetips.htm