I noticed on my Aurora with the 3.5 V6 that its oil pressure has a very LARGE range. When the engine is cold and idling, I have seen as high as 115 PSI. On a warm idle during the summer, I have seen as LOW as 13 PSI!! Just curious if anyone has ever seen a car with such a huge range for the oil pressure. Does anyone have any reason as to why this engine might be that way? I sure don't!

Cold idle, oil pressure.


Warm engine, crusing @ 55MPH


and finally, warm engine, idling @ 550 RPM.

I doubt those are the actual values. Have you hooked up a mechanical oil pressure gage to it yet? You might need a new sending unit, but there'* no way to verify the actual oil pressure without an external gage.

While not knowing your engine well, Toasty had brought his Aurora 4.0 down one day and we were cruising around. He mentioned how the oil pressure at idle was 8psi and considered perfectly normal on this motor.

Being a baby version of the Northstar, I could understand that your 3.5 would have the same crazy looking readings that we are not used to seeing. I never questioned the top end valuves..

I know that the northstars run at almost freighteningly low oil pressure. Like Bill said, when warm and at idle, 8psi wasnt anything abnormal, however, i never saw anything close to 100psi, i think the highest i ever remember seeing was 50ish.
However, i could see if your maybe running a heavy weight oil in cold conditions at higher RPM, that 100psi might be perfectly normal aswell

A failed sending unit would read pegged out at 120 most of the time. The value of my oil pressure on the in-car gauge follows engine temperature and engine RPM exactly as it should. I don't think a bad sender would read both high, and low. Aaron, the odd thing is, I run 5W-30 year round. And you're right about it being considered 'normal,' the service manual states that the "low oil pressure" warning doesn't come on until 5 PSI. I just wonder why these engines run so low. Hmmm. Forever shall remain a mystery.

have you asked around at ACNA? i thought i remember reading a discussion over there about it????

we've talked about how they have low oil pressure, but nobody seems to know why they do. I was hoping that someone would have some insight on what would cause an engine to have low pressure, and why it would be designed that way? I don't know enough about engine design/engineering to know why it would be that way, nor do I know possible causes, either. I was hoping someone would have an idea of why it'd be so low. It'* nto really a technical problem, it'* more of a discussion more than anything else.

Since your engine is similar to a Northstar, it may be best to ask around in a Cadillac forum. I know the oil pressure in our Cadillac is low as well.

http://www.cadillacforums.com/forums/

My dad'* '02 3.5 Aurora has the same readings.