ATF vs. oil chirpy blower motor

[bobjohnston]

Anyone have personal knowledge/ experience on best lubricant for blower motors? My 94 E420 (W124) very occasionally makes a slight chirping over the last few years, then goes away. I'm in deep with evaporator replacement this very moment- sure would be easy to lube the blower motor, but hate to replace it since there is no terrible current problem (later models with dust filter are about $300). I've read posts suggesting ATF, but elsewhere have read that ATF is bad for this as it boils (flashes) off with heat if not in a sealed system. Many have suggested sewing machine oil if sintered bearings are used, as this will actually "soak" into the bushings/ bearings.

So, has anyone had experience with the later blower (with dust filter) to know whether it has sealed bearings, or sintered bushings? What kind of lube? And what about the brushes?

Thanks in advance