Originally Posted by Laughingchi
I have a 100 year old furnace (literally). It is a coal conversion to natural gas with a blower and cabinett fitted to the back. The blower motor and the squirrel cage blower itself have little brass oil cups with covers on the bearings. I had been using motor oil in them but it seems to be running through alot quicker now (used to be once a month now once a week). I tore it down and the bearings seem fine (no slop) and seem to run smooth. I'm thinking of using a heavier grade motor oil so it doesn't run through as fast. Any suggestions on oil weight to use?
I'll say up front I have no intention of replacing this furnace with an upgrade. the furnace is far more reliable than fancy modern high efficiency furnaces that take an arm & a leg to repair. This 100 year old just keeps doin the job & my worse gas cost was a bit over $200 in January.
Sounds horribly inefficient, but not having some computerized control board can be a blessing, too. (Why do those boards burn out at the beginning of the coldest two weeks in winter, and always take two weeks to get shipped to you?)
Now, have your grain of salt ready. The following is my two cents worth of down and dirty farm-style tech.
Having a relatively large amount of old motors around, (mostly on or from old wood working equipment), I'm familiar with oil cups. Every old motor I have seen seems to use a worsted wool wick of some sort to distribute the oil to the bearing. Frequently, with age or the use of the wrong oil, the wicks get gummed or burned up, and really, they just seem to wear out after a while no matter what you do. Every old motor I have encountered that wanted frequent oiling seemed to be in need of new "wicks."
For what it's worth, several of my motors bear plates requesting SAE #20 oil, and the ones that have no special requirements run fine off of the #20. It's not typical motor oil, it's machine oil, and non-detergent. You can find it in a little bottle that says 3-in-One Motor Oil (blue bottle). http://www.3inone.com/products/motor-oil/
It's even handy to apply right from the little squirt bottle it's sold in. Regular 3-in-One will work in a pinch, but it seems to be prone to leaving deposits, which are probably the reason behind your current troubles.
I'm not positive about it, but I have cleaned up a couple of motors that had really gummy bearings that I suspect were from someone using the wrong oil. running them for a while with automatic transmission fluid seemed to do a good job of cleaning them up enough to hold larger amounts of the proper oil. They do not come clean by hand at all, so don't take the motor apart to try it, because they will simply be destroyed in the process. (Been there, done that.)
Maybe do a little Googling. Folks who work on and use a lot of old machine tools and wood working equipment tend to know a lot about electric motors, and you'll find stuff posted all over the Internet about what they've tried and how well it works.