All oil pumps have a pressure relief / adjustment valve. Some are factory set with a spring others can adjust the spring pressure to maintain a more stable pressure at different temps or
rpms
. If the pump wears ,gears /gear cover - has a sticky relief plunger - dirty filter ,,,, these can all reduce pressure and flow .
If your sensor is reading the correct pressure you should see an increase 10-50 / 20-50 oil . I
wouldn't
go any thicker than that . I
don't
think the pump will work any harder with 50 or 60 wt oil - its like a tea to milk increase for the pump . I would worry more about the flow of thicker oil than the pressure.