I have a 2003 350z with just under 150k miles on the dash. I’ve noticed has a much lower oil pressure than it did suddenly. I used to be getting around 60-90 psi at normal highway driving and just under 120 at WOT. Now I’m getting around 30 psi almost all the time. It’s around 15-20 psi at idle. The oil levels seem fine, I changed it 2000 miles ago. It’s right at the halfway full mark. Should I start looking at oil galley gaskets or is that just for the HR motors? Maybe change the oil and check again? What happened? Should I be concerned?

 

Are there any additional mods installed that can have an affect on oil pressure such as an oil catch can or even a non OEM (or old) PCV?
Also what type of oil was used and was the filter replaced?

 

I would start with the oil pressure sensor/ sending unit. You could also get a mechanical gauge and test it at this location as well, to confirm if it's just a gauge or sensor issue.

Your previous oil pressure sounds a bit too high to me, but perhaps the DE engines are different.

If it's not the above mentioned, then you could start looking at a blocked oil pick-up/ passage way, galley gaskets, and oil pump.

 

^ Yup.

Check your FSM to see what the OP should be at warm idle & 2k RPMs (no load most likely). Then check your OEM gauge readings and use a mechanical gauge in place of the OP sending unit to verify if your OEM gauge is wonky or not.

If it is, new OP sending unit should fix the problem. Maybe replace the gauge. At the very least, you will have isolated any mechanical issues.

 

When I did my timing chain I replaced the gallery gaskets too (04 DE), it does sound similar to what happens with those guys with the HR motor.

 

I was under the impression that the DE variant doesn't suffer from the same oil gallery gasket failures as the HR and VHRs, or at least I have never seen a documented case of this happening on a DE. However what is more common on DE platforms is the oil pressure sending unit failing. This seems to be the most common fix for the earlier Zs, I would start there.
-Icer

 

Nothing recent, when I bought the car with around 144k miles I had to buy a new PCV hose from Z1 since the old one was cracking pretty badly. Since then the only thing I have changed on the car is a catback exhaust and replaced all coil packs.
I used castrol edge 5w-30 and a k&n filter

 

Will do. Thanks!

 

From the FSM for '03: