The oil pressure gauge is accurate ........ I checked mine last week ............ but that's exactly what it measures - the pressure NOT the amount of oil .............. the only way to measure the amount of oil in the car is via the dipstick
So surely, less oil mean less pressure? I am not saying only use the gauge...but if you know what the gauge reads normally then if it shows anything different.... check your oil
and I seem to think the "60-60-in sixth" matches what my dipstick reads