Lubricating 4.5V 6216m2 engine
You don't need to open the motor to get the lubricant in. Electric motor oil is thin enough to work in if you hold the motor with the shaft uppermost and slowly rotate the shaft by hand while squirting a small amount down the shaft.

Don't use a lot - try a small amount, and see how well it works. Add more if needed.



(this one I found on Amazon)