Control Fan case with Raspberry Pi 4 Black Case with Fan

Hi I just use Raspberry Pi 4 Black Case with Fan and I want to make the fan smooth cuz my room quite silent, so I try open fan to drop some oil but nowhere to drop - I read some guide have the hole but no hole, in this case, so anyone has a guide to control the fan running only when high temp and make it more silent?

Thanks for any help :slight_smile: