Low Oil Pressure

Troubleshooting
1

Hello all my name is: Peter
I have a: 1991 GTO VR4 TT
It has the following issue: low oil pressure, reading about halfway from L and the mid line when doing ~2krpm and reading just shy of middle at ~3/4krpm

I’m recently rebuilt the engine and am running 5w30 oil. Completely new crank and bearings and seals and really don’t want to ruin the car. Oil pump looked good when rebuilding.

I put upgraded lifters in, would that affect pressure?

Engine isn’t broken in yet if that would change anything

Would love recommendation on oil thickness and brand if yous have any

2

If I’m not mistaken, the oil should be 10/40, semi synthetic. This may account for the problem. Anyone else got any ideas?

3

if you are using the stock gauge it is unreliable. A fresh rebuilt engine should have normal or higher than expected pressure unless you have got your bearing clearances wrong.

as Joe has said standard is 10/30w or 10/40w depending on climate. I have previously rebuilt an engine on another car and the break in period is involved, 1kmiles change 5k miles change, never sitting at the same RPM for too long, lots of driving under vaccum ( throttle closed but in gear). I used millers break in oil but not sure they do the correct weight for this car.

4

mine never really goes past the middle in the 5 years ive had it.

5

#1 5w30 is way too thin. I’d personally run Rotella 15w40
#2 The stock gauge is unreliable. If you want actual reading install in aftermarket gauge.

6

10w40 oil is what Mitsubishi UK used to put in these cars semi or fully synthetic oil. Been running shel helix on both my TT cars for years with good oil pressure :+1:

7

I’ve used synthetic 10w40 without issue (2 oil changes so far) on mine which sat a decade before I got it. The pressure gauge sits a few marks below the midpoint under normal driving conditions. It goes slightly over the midpoint at higher engine speeds like 5th gear on the motorway

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