Necessary to lubricate old electric motor?
YES. In the farm we do it all the time. A bit of grease is better than oil. You can remove the two screws and separate the carriers. In the motors pictured, there should be a bushing, so no ball bearings will be falling out (hopefully)!. Other than the bearings, not much else to fail on these shy of burning up the coils. When you put it back together, lightly tighten the screws, rotate by hand. When snug, power up very briefly. Tighten up, maybe a bit of thread-lock (easy does it) and you should be good for another 20 years!. If you remove the rotor, clean the dust out of the gap too!