Oil pressure

What engine do you have?

What kind of oil are you using?It should be changed every 3K miles with a Toyota oil filter and a good grade of oil. The worst thing you could do is use a Fram or discount store oil flter. The Toyota filter has a check valve that allows constant oil pressure.

If you had ever picked Fram filter parts out of an oiling system you would know what I am talking about.

If you are using a good grade of 10W30 then the oil pressure drop may be due to warn engine components in the oiling system. It could be mains, rods, camshafts or even the oil pump pressure valve. There is a sligt chance that the oil pickup screen migh be clogged. That all depends on the oil change frequency.

It might also be a faulty oil pressure sending unit if every small change makes a pressure change. The sender has a damper that takes the bumps out of the pressure reading so it will be a constant pressure.

Good luck