Originally Posted by Andy W
NEVER oil motors that have ball bearings
This, I believe, is contrary to the information Astro Bob provides. I can't find my instruction sheet for my Mighty Micro 010 so I might be wrong but my personal experience supports the use of oil on ball bearings:
I'm on my 3rd set of bearings in 10 months on my 010. This last set is the first set I've oiled and they have outlasted the last two sets by at least twice as long. They're also noiseless to this day.
Some bearings are actually sealed but many are just shielded. Sealed bearings are "lifetime" lubricated but shielded bearings typically aren't.