I have to admit upfront that I'm ignorant as to what type of bearing the BIX uses. What you describe kind of sounds like temp related issues, but I have a hard time believing that a few degrees difference inside your house between winter and summer could be causing this, at least as it might relate to lubrication. Very strange, indeed.
One experiment you could try is to get a can of freeze spray (Rat Shack maybe?) and some kind of digital temp sensor. Then you have a direct method for cooling down the bearing while watching the temp at the oil bath. Measure the speed with a strobe while the temp is low, then again at a normal room temp in the summer.
One experiment you could try is to get a can of freeze spray (Rat Shack maybe?) and some kind of digital temp sensor. Then you have a direct method for cooling down the bearing while watching the temp at the oil bath. Measure the speed with a strobe while the temp is low, then again at a normal room temp in the summer.