That is another reason i changed it. I did not want to find out
Good luck, and i hope it solves your problem. 15w40 should have given way more pressure though, i find it strange it did not even go up. It should have, even with a worn pump. It should not have been enough, but it should have gone up.
Before you disassemble your engine, try with another pressure sensor and gauge ... maybe the pressure is good but the sensor is not.