Reading Oil pressure gauge on 90 Nissan 300ZX

I don't have a '90 300zx in front of me at the moment, but most engineers design gauges so that "normal" is at the halfway point. A little high or low is OK, but a big variation is cause for concern.

Low oil pressure readings can mean a worm engine or a weak oil pump. High ratings can mean clogged passages in the engine. All this assuming you've changed the oil relatively recently and put in a proper filter.

There may also be more specific things a 300zx gauge tells you - for example, a reading that varies significantly with engines RPM indicates wear - but what specific wear is typical in that motor would be better found by seeking out a web forum specific to Z cars.

I don't have a '90 300zx in front of me at the moment, but most engineers design gauges so that "normal" is at the halfway point. A little high or low is OK, but a big variation is cause for concern.

Low oil pressure readings can mean a worm engine or a weak oil pump. High ratings can mean clogged passages in the engine. All this assuming you've changed the oil relatively recently and put in a proper filter.

There may also be more specific things a 300zx gauge tells you - for example, a reading that varies significantly with engines RPM indicates wear - but what specific wear is typical in that motor would be better found by seeking out a web forum specific to Z cars.

I agree with the "middle of the range" statement, however early Z cars are notorious for very low readings at idle. I don't know if the 90's suffered from this but I doubt it. either way, starting from idle, the pressure should rise somewhat with RPM until it reaches a peak value, then stay constant with more RPM.

if your gauge scale is in PSI the rule of thumb attributed to Smokey Yunick is 10 psi per 1000 rpm as a ballpark figure. if you have less than 60 PSI at 6000 RPM for example, there may be a problem. if the pressure is more than 100 PSI at any time, there also may be a problem (you don't want your oil filter to explode...)

the dashboard gauge can be no more accurate than the sending unit, so we are assuming it is working within design tolerance. if you really want to know the pressure precisely you would need to temporarily replace the sending unit with a mechanical gauge of known accuracy.

these and the comments above assume your engine contains oil of the specification found in the owner's manual and that the engine is warmed to normal operating temperature.

The psi on my 300zx Is low and it takes time to go to second gear will it help if I replace the oil sender??

Mine does the same thing have u figured it out