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Can a Bonneville handle thicker oil? My pressure is still low.

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Old 11-11-2008, 08:24 PM
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Unhappy Can a Bonneville handle thicker oil? My pressure is still low.

I just got it checked at the shop AGAIN [Third time this week]
And they said that it'* probably my Engine Bearings being worn down that'* making my oil pressure so low.

I don't know what they do, but I know it'* expensive to have them fixed.
I paid 1500 for the car 3 months ago, and in the last month I've put almost 1500 into it!
So i'm not going to get those fixed. If it dies, it dies.

But to prolong its life, [and to stop the non-stop dinging at idle that the dashboard makes] can I put thicker oil in? Right now it'* 10-W30 as far as I know. But if I put in 15-W40 in, it should bring the PSI up. Will that be bad for my car? What about straight 20 or 30?

I only think it should be thicker because the pressure is fine when the engine is cool and the oil is thick, but obviously when it warms up it gets thinner, and brings the PSI down.

Also, to put a little more pressure in, I might add a higher-pressure oil filter.

But basically my question is- Can I put thicker oil in my 3800 Series II and have it still run?

[Any ideas on what oil to get in would be great too]
Old 11-12-2008, 07:00 AM
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you can try 'Lucas' brand motor oil additive

http://www.lucasoil.com/products/dis...?iid=4&catid=6

It'* really really thick, and you just add to your motor oil


I can't guaranty anything though

Last edited by Toddster; 11-12-2008 at 07:03 AM.
Old 11-12-2008, 11:20 AM
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Thanks a lot for that link, Toddster.
That'* what I was looking at at my Gulf station today.
How much of that should I put in with my oil full?
Should I drain some oil out? It'* really at almost full, although it leaks a little so it may have gone down. Not sure. Just wondering how much I should put in per-quart of oil in the engine.

[I figure I would ask on here, just to have an idea before I go to the store]
Old 11-12-2008, 11:55 AM
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I really cant believe what some mechanics will tell people. The condition of you engine bearings has Nothing to do with oil pressure. Low oil pressure is caused by 2 things. It'* a sign that the pump has worn to the point it needs replacement. Or there is blockage between the oil pump and the oil sending unit. And that'* about it. While putting thicker oil/additives in it may or may not show you a higher pressure on your gauge, that'* just giving you some temporary peace of mind. What you are really doing is just putting a bandaid on an issue. A bandaid that is just hurting/complicating the original problem. Thicker oil is going to make the car start harder, make it harder to reach critical areas that rely on "splash cups" to get the oil to where it'* needed. Also seals start blowing because some oil passages are not blocked as bad as the one to the oil sending unit. Additives for the most part create sludge. And in the long run make more trouble than you started with. I have seen a multitude of evidence to this on the web. You just cant buy a mechanic in a can, regardless of what slick advertising and misleading test info is posted.

Run a name brand flush in the oil for a day or two and then dump for synthetic and a new filter. If this doesn't help, it may be time to think about replacing the pump.
Old 11-12-2008, 12:05 PM
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I agree with venom here. You can't ignore what is causing it. Get a can of seafoam and follow the oil procedure. This will clean up the lower end of your engine. If there is build up it should clear that out. When doing this your oil pressure will drop, and teh oil will get real watery and very dirty. So change filter and use good synth oil. I strongly suggest Mobile1 5/30 and a good mobile filter.
Old 11-13-2008, 07:42 PM
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Maybe change your oil pressure sending unit to see if that cures the problem. Heavier oil or additives is really only a band aid as previousely mentioned. Higher vis oil (10-40, 20-50) may help things for a while. Expense and degree of difficulty in replcing an oil pump is relative to the person paying for and doing the work. An oil pump is not REAL expensive or hard to install. It is cheaper than having it fail totally and locking up a motor, and sending another Bonnie to the side of the house forever.
Old 11-14-2008, 06:28 AM
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With the low oil pressure reading do you have any knocking or noise when you accelerate from a stop?

I can understand what your mechanic is saying and I can understand what Venom is saying. Seeing both points leads me to want more information. How many miles on the engine etc. What year the car is? How frequently you change the oil and with what oil and which oil filter? How does the oil look when drained, metal flake, grayish streaks?

The way our motors build oil pressure is through the bearings. Our style of oil pump hardly wears and this is one of the reasons for the longevity of the 3800 using this style pump. Your mechanic should be hooking up a mechanical gauge and reading the actual pressure, not relying on your dashboard gauge. From his mention of low oil pressure, that would mean that the dash gauge is reasonably accurate in it'* complaint about pressure.

You can run a thicker oil if you would like. And if the bearings are on their way out, it will help for a short period of time. There is another item to keep in mind. Our motors have a spring and plunger that regulate pressure. By adding a hardened shim between the spring and plunger you can raise pressure while RPM'* are present. This would not help pressure at idle.If that spring broke by some stroke of bad luck, it is possible that some pressure is bleeding past. I would doubt that scenario though.
Old 11-14-2008, 12:45 PM
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It'* definitely not the relief valve on the pump, but it might be the pump itself? I'm not sure.
I have only had the car for a few months, so i'm not sure what the previous owner used, but I got my oil changed twice since i've had it, both times with just the basic pennzoil. I almost did it myself but I don't have the time with school and helping my mom out. So i'm not sure if there are any metal flakes.

I always keep oil in the car, but it does leak oil. but not very much, and i always keep it at almost full.

The car is a '96 SE with about 126K miles on it.

There isn't any noise really, although it'* stalled once since the engine repair, but it started right up again. Also, the other day after I took my foot off the brake, the car moved forward pretty quick, the CHECK OIL light came on [I checked, it'* fine] and the ABS light came on. I figured it was something with the speed sensor maybe? I have a few problems with the front passenger suspension/wheel. Too many pot holes in Pittsburgh
Old 11-25-2008, 08:06 PM
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All good stuff above.. Do you have good oil pressure when you first start the car with a cold engine @ idol ? , oil pressure is the highest with thick cold oil, as the engine oil heats up loose bearings,weak pump and thinner hot oil can lowers pressure alot....I have 2000 cavalier z-24 with a 2.4l, bought the car from a friend with a blown engine,picked up a used one, used engine wasn't right after about 3 months, started hearing ticking at low rpm when engine is hot, tired all types of oils gained really nothing,did flush,tried lucus,seafom....full synthetic....same thing...added a mech oil pressure gauge, cold engine oil pressure 60psi as it heats up, starts dropping after about 20min at engine temp 190deg, idol oil pressure is 30psi, then after about 30min at 190 deg (of driving) drops to 13 psi at Idol (750rpms)
at 2000rpms and above hot engine goes to 30-37 psi....I drive this car to work 33miles one way, so the car doesn't see low rpms (idol) much...been this way for 30k miles. I am positive my problem is worn bearings....Gm say'* 2.4l hot engine at 750 rpms 10 psi is ok and 30psi at 2500rpms per service manual ...so I haven't jumped on changing the oil pump yet, easyer to swap the engine on a 2.4l...this engine burns a quart of oil every 2k...
Old 11-26-2008, 08:22 AM
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These pumps are pretty hearty and don't usually break down much with time and mileage. Most likely it is the pressure relief valve. If that'* that case, I'd pick up an oil pressure increase kit from Intense-Racing.com and install it. Takes probably about an hour as the gasket can be a pain to get off the block. Basically though you remove the passenger tire and splash shield, then the filter adapter is right behind the power steering pump. Four 13mm bolts and it is off the block.


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