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 place a little oil on the bearings to replace what had been "lost" (and usually you could do this ONLY with the FRONT bearing). Often people used WD40 as an light oil easy to get. HOWEVER, modern fan designs usually are so sealed up and securely fastened that you cannot disassemble without breaking things, and re-assembly is nearly impossible. There actually is NO way to reach the bearings, front or back, to add oil. So now people try to just spray oil around and hope it does some good. A LITTLE oil for lubrication only might make sense theoretically except for the fact you cannot direct it to the bearings where it might be needed. A LOT of oil to try to CLEAN makes no sense at all! It is NOT the same as canned air pressure to blow dirt out and leave the fan clean.