My oil pressure gauge is reading above 120 psi, even when i turn my car on...I then got my oil changed and it didn't change...can anyone explain some of the reasons why it is that high?

Is the car "new to you"? If it isn't, has the pressure been like this before (I'm guessing no)? If it is new to you try and contact the previous owner and get an answer.

Your oil pressure will always be higher when you start the car than after it has been running because the oil is cooler. Cooler oil is more viscous and will result in a higher pressure reading. As it warms up it will thin out and the pressure should drop. What weight oil did you use? Nissan recommends 5w30, a thicker oil will also make the pressure higher than normal. Even though 120psi sounds high it's not unheard of. Here's a link from a similar situation from three years ago.

It could be something as simple as a stuck gauge or a bad oil pressure sending unit. To check your your sending unit turn the key to the ACC position, Do Not Start the Car - the oil pressure gauge should remain at ZERO. If it shows any reading when the engine is not running then you know where your problem is.

Make sure to check your oil before you start your car...
1) It gives you an accurate reading from a cold oil temperature.
2) If you were running excess oil psi there is the potential of a leak, better to find out before you start it up.

Keep us posted about what's going on.

And welcome to NICO!

yes i just bought the car on monday, and honestly i never really paid attention to it til a couple days ago and noticed it was above 120 all the time...im gonna go try the acc thing real quick

and thank you...this website is very helpful

so i tried the acc thing and the pressure indicates above 120 psi...so is that the gauge that's gone bad?

No, the sensor/sending unit - the piece that actually senses the pressure and sends the signal to the gauge on your dash.

Here's a link to the 350Z FSMs (Factory Service Manuals). I don't know what year you have or I would have linked you to the correct year.

If you're mechanically inclined you could change it out yourself, but you'll need to get under the car. Here's where you can buy it online. If you're not able or don't want to do it yourself you can always just take it to a shop.

You'll need to drain your oil to do it, so you can either live with it like it is (I'd still be checking my oil more frequently than normal and really being attentive to how the car was behaving) or you can drain it and change it out for the peace of mind (what I'd do, but I'm like that!).

Here's a diagram from the FSM of the oil pressure sensor/sending unit unit location. You'll need to remove the undertray to get to get to it.

I recently rebuilt my motor and have the same issue. I verified my sender is correct with an external gauge and have ordered oil pressure and temp gauges. I have a Mocal sandwich plate for my Setrab cooler and am looking for a means to add the two sender units the pressure and temp gauges will need. Thanks in advance.