: Low oil pressure?



blsnelling
04-15-04, 10:28 PM
I have a '97 Olds Aurora with the 4.0L Northstar. With 10w-30, I'm only getting 9-11 psi oil pressure at idle. At 2000 RPM it's about 42 psi. At 1500 RPM it's about 30 psi. The manual specs a minimum at idle of 5 psi and 35 psi at 2000 RPM. I know I'm above the manual minimum, but this seems like awefully low oil pressure. Is this anything to worry about. I have replaced the sending unit with no change. 10w-40 added a couple psi, but nothing major. Could the springs in the relief valves in the oil filter adapter be weak, causing my oil pressure to be lower?

STS
04-15-04, 10:34 PM
um, why do i feel like you don't have an issue?

blsnelling
04-15-04, 10:48 PM
Take it easy on me.:worship::) I'm a nubie on the forum here. Yes, I know I just quoted you the manual specs. The problem is that I'm used to seeing greater than 30 psi oil pressures at idle. This includes several GM 3800s, 350 SBC, and 5.3L in my GMC truck. I just want to know what oil pressure most others here see at hot idle in gear and stopped.

STS
04-16-04, 12:03 AM
my 468BBC only sees about 8psi at idle.

RBraczyk
04-16-04, 06:25 AM
My 1994 Blazer, K1500 Full size sees about five psi at idle. As the vehicle gets older, the Oil pump doesn't work as well as it used to. Don't worry about it, you should be fine. Plus your seals get hard and don't work as well, so thats a factor too.

Lawrence
04-16-04, 11:39 AM
Agreed, you have nothing to worry about there. A new engine would have no better pressure.

blsnelling
04-16-04, 12:37 PM
A new engine would have no better pressure.Now that's what I like to hear, even if it's a lie.:) Thanks for all the responses, everyone.

El Dobro
04-16-04, 01:04 PM
You may want to put 10w-30 oil back in too. GM doesn't recommend using 10w-40 in their gas engines.

blsnelling
04-16-04, 01:43 PM
Just put Amsoil 10w-30 in it last night. The 10w-40 was Amsoil as well.

BeelzeBob
04-16-04, 01:57 PM
I have a '97 Olds Aurora with the 4.0L Northstar. With 10w-30, I'm only getting 9-11 psi oil pressure at idle. At 2000 RPM it's about 42 psi. At 1500 RPM it's about 30 psi. The manual specs a minimum at idle of 5 psi and 35 psi at 2000 RPM. I know I'm above the manual minimum, but this seems like awefully low oil pressure. Is this anything to worry about. I have replaced the sending unit with no change. 10w-40 added a couple psi, but nothing major. Could the springs in the relief valves in the oil filter adapter be weak, causing my oil pressure to be lower?

Your oil pressure is fine. The engine needs little to no oil pressure at idle. Extra oil pressure just wastes energy...i.e...costs fuel economy. So....there is very little oil pressure at idle by design with the Northstar/Aurora engines. Relax and turn off the oil pressure on the DIC....LOL.

blsnelling
04-16-04, 03:01 PM
Thanks for the confirmation. Do you recommend against the 10w-40, even in a synthetic, as it isn't as likely to shear and cause ring pack problems as a dyno 10w-40? I know your feelings on synthetic as a whole.

BeelzeBob
04-16-04, 03:30 PM
Current 10W40 oils are not nearly as bad as the old 10W40 oils that caused all the problems back in the 70's and early 80's ...but....I still wouldn't really recommend it. The engine oil pressure bypass control circuit is sized and set up for 10W30 and it will not control as well with 10W40. In reality, to pass the SL requirements, the 10W40 oils cannot have nearly the percentage of Viscosity Improvers that they really need to be true 10W40 oils so most current 10W40 oils are on the verge of being 10W30 oils anyway.... There really is no real reason for 10W40 oil....just the perception from the public that 10W40 oil is somehow "better" so they want it and buy it and the companies continue to market it to supply the demand for it. If a 40 weight oil is really necessary due to bearing clearances or whatever then a 15W40 is a much better compromise as the 15W40 blend requires much less viscosity improver due to the higher viscosity base stock. To meet the SL performance requirements everybodies viscosity improver package is a synthetic anyway....so all the SL oils are synthetic "blends" to some extent and a snthetic 10W40 has no advantage over a conventional 10W40 oil as BOTH have synthetic viscosity improvers.


I'm constantly being misunderstood on synthetics. They are excellent products and cause no real performance problems. I am not against them per se....I just want people to understand what the synthetics do (provide ultra high temp capabilty without breaking down), that synthetics are NOT required for the Northstar engine (prior to the 2004 RWD engine with VVT) and that synthetics do NOT allow extended drain intervals or anything. Used in this context, I have nothing against synthetic oil at all....as long as people understand that using synthetic in the older Northstars will tend to exacerbate any oil leaks.

I do have a REAL PROBLEM with Amsoil in general in that they keep insisting that their oil allows much longer change intervals....which is NOT true. If the ONLY thing that mandated an oil change was high temp oxidation (evidenced by the sequence 3E testing that Amsoil loves to quote) then they might have a case...but high temp oxidation is rarely if ever the reason the oil needs to be changed. They seem to forget about ZDP depletion, oil contamination with gas and water and other contaminants, petane insoluable contaminants (carbon, soot, dust, dirt) and other reasons that oil needs to be changed. Last time I checked (admittedly some months ago) their latest and greatest synthetic was not even GF3 or GF4 approved but that may have changed. Their insistence on advertising the longer change intervals is the reason that they have very little credibility with the OEM's.

RBraczyk
04-20-04, 07:48 AM
Change the PCV valve, it usually increases oil pressure. It worked for my blazer, its starting to see around 10 psi idle.

El Dobro
04-21-04, 03:13 PM
The PCV is for venting the crankcase. I don't see how it's going to change oil pressure.