Broan-NuTone N-8664RP Combination Light Fan Exhaust Fan "noisy throw bearing" Questions

15 year old bath fan/light noisy. rectangular 2 bulb model 164A-D Could be that dirt and dust have collected on the fins over the years and are throwing them out of balance. You could try cleaning the

...noisy & the rather brief instructions say to NOT oil the motor. I would appreciate any suggestions on how to remedy this situations. They were a bit expense & I'd rather not replace them... ...