Oil Pressure Gauge

Either the gauge system is failing or the oil pressure relief valve is stuck closed. The thing to so is to remove the oil pressure sending unit and screw in a mechanical test gauge. If the oil pressure runs about 40 to 60 lbs revved up and idles about 25 to 35 lbs it's probably OK (these are typical figures). If it goes up high (80 to 120 lbs) when you rev the engine up then the pressure is not being controlled by the relief valve. That could damage your engine, and should be addressed ASAP. If the oil pressure is normal, then the gauge system has failed. Most likely and easiest to fix is that the pressure sending unit has failed. Here's a directory link for you: http://repairpal.com/nissan-repair-in-walterboro-south-carolina