Interestingly, not one vintage Singer manual that I've read mentions using grease on gears. They all clearly describe sewing machine oil only.
As for motors, after a lot of research, I'm definitely going to try Vaseline (I'm not recommending you do the same. That's your decision to make.
)
Here's just one article I've come across:
http://archaicarcane.com/a-search-fo...e-replacement/