Borderline Low Oil Pressure, Normal? - Page 2 - GM Forum - Buick, Cadillac, Chev, Olds, GMC & Pontiac chat


1992-1999 Series I L27 (1992-1994 SE,SLE, SSE) & Series II L36 (1995-1999 SE, SSE, SLE) and common problems for the Series I and II L67 (all supercharged models 92-99) Including Olds 88's, Olds LSS's and Buick Lesabres Please use General Chat for non-mechanical issues, and Performance and Brainstorming for improvements.

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Old 05-13-2007, 02:28 PM   #11
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You may not want to hear this, but......Low oil pressure is typically caused by increased oil clearance between the engine bearings and shaft journals as the engine wears. Lower viscosity oils (5W-30) and high engine temperatures will drop oil pressure further. To increase oil pressure, you can run heavier weight oil (15W-40, 20W-50); and keep engine temperatures down by installing a transmission cooler, lower temperature thermostat, and making sure that your cooling system is in good shape.

Sometimes, the spring in the relief valve weakens resulting in lower oil pressure, or the oil sending unit becomes inaccurate and needs to be changed, but most often it'* the bearings.
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Old 05-13-2007, 03:32 PM   #12
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Typically how much would it cost to rebuild the bottom end? And how long would the engine last in this condition?
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Old 05-13-2007, 03:43 PM   #13
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My oil pressure hovers around 25 at idle, always has though, even on my 93, it did the same thing, im around 55 on the highway though
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Old 05-13-2007, 03:50 PM   #14
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when my car is fully hot and been running for a while at idle im around that 25-35 mark...

at like 1,300 RPMs im at 45ish. and at 2K + RPMs im at 55ish

this is all if my gauge is right
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Old 05-13-2007, 05:30 PM   #15
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I believe the issue is directly related to the transmission temp..from 200-225* it seems to have the low oil pressure issue, even at 150 the idle oil pressure is around 55psi. Crusing is upwards near 60 on the dash gauge


Rebuilding the lower end is a risky option in my opinion unless you do everything right and have an engine builder that knows what they are doing. I have a 60K L67 from a 98 park ave that I've talked to the JY about, the only problem is I dont have a truck to get the motor from there to here to swap.

However, the car runs perfect right now with no evidence of ticking or knocking noises in the slightest so it may just be normal wear and tear for the miles. I'm thinking about 15w40 next time I do an oil change. I dont see it hurting anything with the temps the way they are, winter I can see a big problem with but its hot now.
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Old 05-13-2007, 06:29 PM   #16
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Quote:
Originally Posted by Hans
I'm thinking about 15w40 next time I do an oil change. I dont see it hurting anything with the temps the way they are, winter I can see a big problem with but its hot now.
I think this is a problem whose severity is exaggerated because information in the owner'* manual intended for a new, tight engine is applied to older cars with worn engines. There is a trade-off to using heavier oils. Lighter oils get to the space between bearings and journals more quickly than heavier oils after start-up. But the film strength is typically better with heavier oils, especially straight weight oils, meaning that a thin film remaining on engine parts protects better than lighter oils immediately after start-up.

Of some 150 or more cars that I have owned, (lost count by now) most of them over 100,000 mi, I cannot remember any failing to start from running heavy oils in the winter, even in below 0*F temperatures. I like to run Shell Rotella T 15W-40 in older, loose engines. Not saying the engine isn't more difficult to turn over, or that it will never cause a problem, just what my experience has been.

Also, just because an engine has 100,000 miles on it, does not mean it will benefit from heavier oil. Some well made and well maintained engines show remarkably little wear and maintain normal oil pressures well past 200,000 miles. The engine that does benefit is the one whose pressure drops because of bearing wear.

When I lived in West Virginia, I bought a rusty, Fiat 124 sport coupe for $50 that showed less than 10 psi oil pressure on the gauge with 10W-30. I filled it with Lubriplate straight 50 weight motor oil with "liquid zinc." The pressure came up to normal and stayed there. I drove it for a year including a trip to Niagara falls with no troubles. On the coldest days, it would turn over easily and start, with the rpms at about 1000, then as the oil pump strained to suck up and move that molasses out of the pan and through the oil gallery, the rpms would drop and the pressure would build way past 40 'til the relief valve opened. The car literally fell apart from rust, but the engine never failed.

Although cars with low oil pressure and worn bearings can often be carefully driven for many more miles, it must be understood that bearing failure is imminent. Engines in such condition should never be subjected to heavy loads or high engine speeds. Wide open throttle use is likely to result in a spun rod bearing. If at all possible, the best course is to replace the worn bearings and shafts as needed to bring the oil clearances back to spec.
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Old 05-14-2007, 12:25 AM   #17
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My oil pressure dropped at an accelerating rate. Took a few years to get below 20 from 25, but since then, it'* dropped in a 1/4 the time and I've got metal in the oil now.
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Old 05-14-2007, 12:27 AM   #18
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Just to post what i've done in the past...

I've taken notice myself in my personal experience that a higher-end oil filter will help the oil pressure. I now use a K&N compared to the Valvoline I was using and the pressure at hot idle is a good amount higher than it used to be. When I was nearing the end of an oil change (meaning needing another) I would notice way lower oil pressure with the valvoline, now with the K&N at the near need for another oil change it'* still high. Try that for starters, if i'm wrong i'm wrong, but that'* what I've noticed
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Old 05-14-2007, 12:31 AM   #19
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I'm not sure how your theory applies to a car that has habitual low pressure at all times.

And on the counterpoint, my two cars don't vary in oil pressure based on oil or filter life at all.
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Old 05-14-2007, 12:46 AM   #20
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Quote:
Originally Posted by willwren
I'm not sure how your theory applies to a car that has habitual low pressure at all times.

And on the counterpoint, my two cars don't vary in oil pressure based on oil or filter life at all.
It never dropped below 40 today as most days but the trans never got above 175.

Its very difficult to get it that low, I got those pics after several tripple digit trans testing runs. Normal city driving the gauge will not go below 40. Same story on the 93.

Regardless an engine swap is not all that difficult for me to do. I've helped swap two 3800s in the past 6 months for grand prixs so its no biggie. Trans is my biggest concern and its getting built up as much as I can afford.

I dont fully understand the correlation between trans temp and oil pressure but its related is all I can tell.
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