Loosen p-trap nut

I have been having problems with the sink draining properly lately. On the weekend finally attempted to fix it. The house is 30 years old and I could tell that the p trap has probably never been cleaned before. The cap on the p trap was hard to loosen so I sprayed some WD40 on it and waited a few minutes so it could lubricate and penetrate the connection.

After a few minutes I could easily loosen the cap in order to clean out the p trap and find out what issues was causing the draining problem. After some time working on the drain, it seems to be working a lot better now. Thanks WD40!!