Oil Pressure increases as the engine rpm, and consequently the oil pump rpm, increases. The oil pressure also increases under all conditions if you use a higher viscosity oil. Conversely, oil pressure decreases with engine rpm and oil viscosity, which in turn decreases with temperature.
So the lowest oil pressure will be at idle when the engine is hot and should be at least 16 psi. This number will above 36 psi when the engine is cold and be 60–80 psi around 4,000 rpm.