I’ve been noticing lately that oil pressure is a little lower than where it has been. I drive the highway every day to work and at 3500 rpm my oil pressure gauge has been a rock steady 50 psi and now I’m about 45 psi. Crankcase is full and change my oil every 3000 miles. Car has 160,xxx miles on it. What does this mean?

 

any changes in oil viscosity? could be the oil pump going out, or maybe the gauge is faulty. Other than that or a leak, I can't think of anything else that would cause decreased oil pressure.

 

I would suspect the sensor... I have heard people saying the oil pump going out but I find it hard to believe the most well lubricated part in the system would fail... get weak maybe but fail??...

 

If it's an electrical gauge it's quite possibly the sensor. They can go out of calibration due to heat (like from the nearby exhaust manifold) over time. This is why some people run mechanical gauges (oil line through the firewall all the way to the gauge in the cabin) or they run an oil line from the sensor mounting location to an electrical sensor in a cooler spot within the engine bay.

Maybe swap out the sensor (not cheap but not insane power steering pump money either) with a new one, or swap in a mechanical local gauge and see what it runs at 3500 rpm. In general you should have a minimum of 10PSI for each 1000 rpm. If it keeps trending downward over time, could be oil pump or the relief valve or drain back valve inside the filter housing.

 

Ok thanks, yes I have mounted my sensor on the right upper firewall away from the manifold.