My (almost 7 year old) MacBook Pro recently starting making a very loud noise. It sounded like it was turning on its turbo booster for interstellar space travel. Based on prior experience I could tell it was one of the fans. I used SMC fan control to confirm my suspicion. The right fan was only reaching about 1,000 rpm. I have had this replaced in the past and knew it would cost about $100 to fix. Since I don’t have money to burn, I decided to pop it open and use a little (or a lot) of WD40 to remedy the situation.
So how did it turn out? My (short term) fix has worked and so far there have been no issues.