said by Jack_in_VA:Maybe not. Some better fan motors have sealed ball bearings. If it doesn't have oil ports or grease fittings it is not meant to be lubed.
That looks like a 36" Air King if so I have one I dumpster dived, the reason it was chucked was the motor barely turned and having noting to lose I popped the motor open and found what ever was used as a lubricant had gelled into something that looked like yellow dog poop. There was some damage to the bushings but not a lot so I cleaned up the front and rear motor shafts wiped and oiled the bushings with some 30W I had on the shelf, I also oiled the felts but they where pretty ugly so I am not sure how much that helped, none the less that was a couple of summers back and the fan is still blowing.
Now that stated that motor is most definitely sealed, that is to say it has no external oil ports but that is controlled obsolescence and one way around that is a regular lubing of the bushings more so once the puppy mother seizes up.