I currently have 10w30 high mileage in my 1985 NA 300zx and this oil changed happened less then 700 miles ago. I'm at 50 psi and when given throttle it'll go to 80 psi. My oil pressure use to be less then that, so I was just wondering if this is normal oil pressure or not?

 

Very high and weird. Might start by switching out the oil pressure sensor/sending unit to verify correct reading. Get OEM part if you can. Screws in by the oil pan, plugs into the harness. Two minutes labor. Please report back on this!

Our Z pros will have some input for you. Meanwhile, do everyone a favor. Sign in, go to User CP menu (upper left), click Edit Signature and add your Z model, year, shifter, turbo or NA, etc. Saves you having to add it to every post. (Guys here go crazy if you don't lock your Q to your specific Z every time you post...They just ignore questions without enough info) Then click Edit Avatar and add a little Z pic under your nick. Cool. You are solid here.

DL a free factory service manual if you don't have it - at http://www.xenonz31.com/reference.html Other free docs there too. Great inspection and troubleshooting pages in the FSM that are easy to follow.

Thanks.

 

Could be a bad oil pressure sending unit (which actually screws into a port on the block casting behind the oil filter), or it could be the oil pressure regulator valve is sticking. To diagnose you need to remove the pressure sending unit and replace it with a mechanical gauge. If the pressure values on the mechanical gauge are close to those on the attached chart (from the FSM), then you do need a new pressure sending unit. If the mechanical values are still too high, get a copy of the FSM and read up on servicing the pressure regulator valve.

 

OEM oil pressure sending unit is the only reliable one. All aftermarket one have shown to be inaccurate.

 

The oil pressure depends on many things but mostly on the oil temperature.