Grease or oil on the caged bearings?

Interesting question, I took off looking up the exact purpose of the cage in a caged bearing and found a lot of info that was new to me, and never really thought about.  When it comes to lubrication the old saw was,  if it slides grease it, if it rolls, oil it.  But that does not apply in many things beyond the M1 Garand I think.  I am not sure there is a way to lubricate something that will last forever.  I have an old school BIC turntable, and I have tried every grease known to man, and the spindle bearing will always turn a color or the grease coagulate into stuff that is the opposite of grease.  The purpose of a sealed bearing is to let it be advertised to last forever, but that is for normal folks 'ever'.   I have replaced many a forever sealed bearing in stuff I keep much beyond everybody elses forever.  That sealed idler pulley on your engine for the serpentine belt is supposed to last the life of the car, but not when you keep it and use it for 30 years.  I have used Lucas high speed synthetic wheel bearing grease, plain 'ol white lithium, Lubriplate,  Moly EP grease and still have a tub of Quaker State wheel bearing and water pump  grease that has the fibers in it, not very usable for our model stuff though, and oil, both synthetic and petroleum based, where I am somewhat partial to the synthetic for my HO stuff, but with the larger O gauge, I like the real thing.  At some point, a bearing will need to be cleaned if it stays in use long enough and if you can find the info from the manufacturer on a particular bearing, he will tell you exactly what to use and how often.

On that motor the ball bearings are there to handle the thrust load applied by the worm powering the worm wheel.  With the motor out of the truck there is no load on the balls and if the clearance, up to 0.010” , is at the end you can see, the balls may not be turning. Real world worm drive gear boxes run in an oil bath.   This discussion has come up before and it was stated at that time that no model train had ever been built with an oil filled gear box.  Those Lionel ball thrust bearings run dry for years with little wear or damage. If the balls were oiled, I think the oil would get spun out fairly quickly and reoiling without disassembly is not possible.   Grease is oil in a carrier that tries to hold the oil at the location where it is needed.   In this case the goal is to keep a coat of light oil on the steel balls. I believe that the Red n Tacky does a good job of this.  I see no advantage for additives like Moly in this application. Oil and grease do add resistance the motor has to over come. Best example of this is modern cars going from 30 weight to 0 weight oil to increase gas mileage.  On the Pullmor motors Lionel put more effort into keeping oil on the bronze bearings handling the rotation. They used Oilite bearings and many of the motors have provisions to reoil these bearings. Very little wear on these bronze bearings can cause the shaft to vibrate and reduce the power and speed of the motor. On these bearings, clearance of less than 0.001” can result in the best operation.