I don't understand why anyone advises "cleaning" a fan with a spray of a light-viscosity oil! The only way such a process could actually contribute to removal of dirt is is you totally soak the innards with oil so it dissolves the crud, and then push more oil through to flush all the dirty oil out. THEN all you have is a motor filled with oil that never should have been there. No wonder it does not work!
I suspect this originates from long ago (at least 2 decades) with older fan designs where you actually could disassemble the fan, clean dirt off the bearing surfaces, add a tiny amount of suitable light LUBRICATING oil (I used sewing machine oil), and re-assemble. For the less handy this was simplified into no disassembly, just try to...