Oil pressure too low? - GM Forum - Buick, Cadillac, Chev, Olds, GMC & Pontiac chat


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Old 03-12-2008, 09:34 AM   #1
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Default Oil pressure too low?

I think the oil pressure in my 96 SE w/ 152k gets me a little bit nervous these days. In the cold morning of ~ 25 F, it starts at ~ 60. After a good run, at highway speed it'* only at ~35 (just slightly lower than the 40 mark). After 60 miles on highway, at idle on gear, only ~ 25 and the needle is shaking a little bit, sometimes. It'* still quite far from the red zone but I don't feel comfortable in this way.

The car has 50% valvoline maxlife synthetic 5W30 and 50% valvoline synpower (also synthetic) 5W30 in it w/ an advanced auto part oil filter (said to be really good one but pretty cheap in price). It only has 1500 miles in this oil and filter. Right after the oil change, the oil pressure was at least ~10 psi higher in any condition. In the last month, the car was used mostly in cold michigan weather, 5 miles each way to work on smooth traffic, i.e, pretty harsh condition to the oil. I just got it back for my ~60 miles one way daily commute last week.

The car went through a UIM/LIM leak ~ 8 months and ~15000 miles ago. It drives very smoothly currently.

So what do you think? Should I really worry? Thank you very much!
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Old 03-12-2008, 10:11 AM   #2
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Sounds like the shakiness may be from a tired oil pressure sender.. as long as you are running at 60 Psi at road speed and 25 Psi at hot idle I'd say you are ok...

My original 95 motor did this as well... My replacement 96 seems to have higher pressure across the board..

Not sure what to tell you at this point..

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Old 03-12-2008, 10:35 AM   #3
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Thanks! But like I said, it'* only at ~35 psi at highway speed after a good run on at 70 mph, :( . So...
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Old 03-12-2008, 01:10 PM   #4
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The change in pressure over time you describe may indicate that you have a leaky injector diluting the oil with gasoline. You can send the oil for analysis to Blackstone test labs for $22.50 and find out for sure.

http://www.blackstone-labs.com/free_test_kit.html

[edit: thanks for the correction, willwren]

I run 15W-30 in my '95 @ 155K miles. The oil clearances on my bearings have increased over the years to the point where 5W-30 would be unable to build normal pressures. Winter temperatures where I live get to about -15F, but I have not had trouble starting with 15W-40.

How hot does the car run? A 180F thermostat will lower engine temperature, increase oil viscosity and increase oil pressure. A transmission cooler will also increase engine oil pressure because it lowers coolant temperature coming from the radiator. I know, it doesn't seem like it should if the cooling system and thermostat are working properly, but experience has shown me that it does.

I am a firm believer that older, worn engines benefit from heavier oil. Many years ago I kept a very tired Fiat 124 running for a couple of years on straight 50-weight oil and STP. When I purchased the car for $50, the oil pressure was so low with regular 10W-30 oil, it did not register on the gauge. You pay a price in fuel economy with heavier oil, but gain in engine (bearing) protection.
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Old 03-12-2008, 01:18 PM   #5
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BlackSTONE labs. And they send the kits out for free. No charge until the analysis is done.

Good idea to send it in and see. But that'* not BAD oil pressure. It'* not GREAT, but not bad. Consider the INTENSE oil pressure kit. Works great. I have pretty good pressure on the SLE without the kit, and 10-15 higher on the Zilla with it.
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Old 03-12-2008, 01:36 PM   #6
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I just sent in for the kit, my last sample was 2 years ago. Thanks for the link.
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Old 03-12-2008, 10:52 PM   #7
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Thanks for the tips, guys!

To your question, Bill, the coolant temp never goes beyond 200F, except on the days with UIM/LIM problems. Now it'* still pretty cool outside, it'* at most 190, if not 180.
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