Rebuilding larger motors I've used silicon/dielectric grease since it doesn't evaporate as much as petroleum oils/greases ,won't effect plastic parts and is far more water resistant.I wonder if it would work as well on these smaller motors .
Silicone anywhere in a dc motor can be a very bad idea.
I something discovered years ago, the hard way, when brush life became a constant problem on larger industrial dc motors. We were using food grade silicone in open heated water baths as a release agent. This resulted in silicone being introduced into the force ventilated dc motors in the ppm range.
Over several months, this led to motor failures when then brushes wore down to the shunts in weeks rather than years. After much pain and suffering, it was discovered (but known to some dc motor experts) the problem was the silicone. When it makes its it way to the brush-commutator interface, it may oxidize with the heat and you’ll end up with bits of things that resemble silicon carbide. The oxides embed themselves in the soft carbon and threading of the commutator follows. Then the brush wear accelerates very quickly and results in total failure when not caught in time.
I don’t know how factual this is but one of the dc motor old timers I encountered that knew about the silicone problem also mentioned that back in the sixties, Western Electric had prohibited silicone as a lubricant in any process that supplied parts that ending up in telephone switching stations. The reasoning was that silicone migrates everywhere and when it makes its way into the contacts of relays, it leads to shortened contact life due the wear caused by the oxides created in an arcing environment.