Burning (?) oil: Long-term issues?

[Benzadmiral]

Hello, all,

The '03 Buick PA, 79,500 miles, has been losing or using oil for a while now. It used to eat ~1 qt. of 5w30 in 4000 miles. After I went with Castrol Edge this spring, it jumped to 1 qt./1200. Now, on MobilClean 5000 10w30, it's slowed to 1 qt./1700. No leaks that I can see; nor could my regular mechanic when he had it up on a hoist. On my other thread, I got the recommendation to do a compression and leakdown test, which'll tell me, if I understood it right, whether oil was getting into the cylinders and being burned.

Okay. Suppose I am burning this oil. I will probably keep this car for a good while. If I balance the cost of replacing valve seals (e.g.) against adding a $3 quart of oil every two months, the latter will win -- unless the car's long-term driveability will be damaged. Will the oil-burning affect my gas mileage (I'm getting good mpg on non-ethanol gas right now), or the smoothness and power of the engine? Will it eventually ruin my catalytic converter?

What's the prognosis, Doctors House, Foreman, and Thirteen?

 

[jorton]

Another member said he solved his burning problem when he tried Mobil 1 0w-40.

Another member says Quaker State Red Bottle is designed for high mileage GM push rod engines.

 

[IndyIan]

Maybe check the plugs to see if all the oil is going into one cylinder, which might be a problem. In your climate 15W40 should be fine too if you want to get serious about slowing a leak or burning.

 

[addyguy]

I'd try a HM 10w30 or even 10W-40 oil first.

 

[sciphi]

Supposing you're burning oil, have you tried running a quart of MMO as a top-up? With the vaunted "cleaning" abilities, it just may help.

FWIW, I've gone 5k miles on Castrol EDGE 5w30 with it losing half a quart. I know the oil pan gasket is leaking just a hair.

Please let me know if this is outside what you want to discuss here, but have you checked or replaced your valve cover gaskets, and made sure your RTV-sealed oil pan isn't leaking? PCV system clogged up?

 

[rslifkin]

With only 80k miles, I'd tend to agree that something is likely wrong. Definitely check the PCV and oil pan as mentioned above. I agree with Schiphi that MMO may be worth a shot. It could be gummed up rings causing the consumption.

 

[demarpaint]

Originally Posted By: rslifkin
With only 80k miles, I'd tend to agree that something is likely wrong. Definitely check the PCV and oil pan as mentioned above. I agree with Schiphi that MMO may be worth a shot. It could be gummed up rings causing the consumption.


I'm with them. I also found if wear is part of the problem the addition of TCW3 into the gas might help. It did with my Aerostar. Just a thought.

As far as long term issues, you could start fouling plugs and ruin the Cat Converter, but I doubt it.

 

[Scott_Tucker]

I wouldn't bother with a leak down or compression test it won't tell you anything about an oil consumption problem unless your engine us running poorly. The compression rings don't control oil and the oil control ring don't seal compression.

 

[sciphi]

The PCV system on the Series II 3800 is dirt-simple. It's simply a white plastic tube running down 2/3 of the length of the upper intake manifold to the PCV valve at the end of the intake manifold opposite the throttle body. The PCV valve is a $3 part that takes 10 minutes and a pair of pliers to change. I could see that white plastic tube getting gummed up and not flowing enough, which would cause the consumption you're describing. Some Seafoam Deep Creep or other safely-burnable cleaner applied liberally down that tube to clean out any accumulation and a new PCV valve would be my first two steps to solving that. Cost for the Deep Creep and PCV valve would be about $15.

The tube is visible upon removal of the PCV valve cover and MAP sensor. It's the small hole to the right of the PCV valve.

 

[Benzadmiral]

Originally Posted By: Scott_Tucker
I wouldn't bother with a leak down or compression test it won't tell you anything about an oil consumption problem unless your engine us running poorly. The compression rings don't control oil and the oil control ring don't seal compression.

Well, maybe I misunderstood the advice. If I know my mechanic, who's always tried to save me money, he'll probably say the same thing as you are.

Sciphi, yes, I've examined the valve cover gasket area in the front. If anything was leaking, I'd see it and smell it on the exhaust pipes, which are right below the gasket. However, I can't see behind the engine, the firewall side. But I've put the car up on the curb and checked underneath. Grime, of course, but no oily wetness. And when Kevin had it up for the most recent oil change, he couldn't spot anything. So maybe I should pop a pint of MMO into the crankcase next time it's low, and another pint after that? How long should I run that mix? The current oil has about 1900 miles on it now.

I've changed the PCV valve twice -- once soon after I got the car in '07, and the second time after two years, last August. Both parts were OEM. If it could have gotten clogged since then, I can replace it a third time. Where can I buy Seafoam Deep Creep? O'Reilly's?

 

[demarpaint]

I doubt it is the PCV valve since you were smart and used OEM. Just be certain the hose is not plugged up. You have 1900 miles on the the oil, I would add a pint of MMO ASAP, and use another pint as top up oil. When you are due for a change run a qt of MMO for the full OCI. Trust me it is not going to harm your engine! If the rings are sticking that should free them up. Just keep an eye on the oil level with the MMO added you might use a bit more.

If for some reason you can't resolve the issue I would have a look at valve seals, or consider using something like Schaeffer's #132. It is another oil additive that has some real value!

To look at the VC gasket that is close to the fire wall see if you can slip a mechanics mirror back there and have a look.

 

[sciphi]

Any big parts store should have Deep Creep.

The VC gaskets can seep while not looking wet. Mine sure did that. Some seepage is typical on a 3800.

And, how is your coolant level? Something has me coming back to intake manifold gaskets, even though that's not a problem.

To test if the PCV is clogged, one could take off the oil fill cap while the engine is idling. A giant sucking sound would be improper, while some airflow would be normal. If I'm recalling that correctly.

 

[Benzadmiral]

Originally Posted By: sciphi
. . . To test if the PCV is clogged, one could take off the oil fill cap while the engine is idling. A giant sucking sound would be improper, while some airflow would be normal. If I'm recalling that correctly.

I tried that, and no giant sucking noise. Yesterday, I took out the PCV valve, which was a little greasy but not caked up with oil. It still rattled. I soaked it in Seafoam then put it, with its little black o-ring, back, then squirted about an ounce of Seafoam into that little hole to the right of the valve. (Not with the engine running, though; is it necessary to do that? With the engine on, removing that housing to reveal the valve does result in quite the sucking roar, and the engine stumbled a bit.)

After a few minutes, I started the car. No white smoke, but I drove it in 3rd gear for about 15 minutes, including up a fairly steep bridge, and back. The car started sweetly as always and drove calmly and smoothly into work this morning.

 

[addyguy]

If I understand you from other posts, this car gets used for daily traffic creeping in a major city, right?

Is there any chance that this low-speed used has 'gummed up' the engine, and maybe a good old-fashioned Italain tune-up is in order?

I know, I know, revving the heck out of an engine doesn't fix everything, but sometime it helps.....

I'd be inclined to add some MMO to the oil, do a Seafaom treatment throuigh a vacumn line, and then run the wee out of it for a while on the highway.....might make a world of difference!

 

[Benzadmiral]

Originally Posted By: addyguy
If I understand you from other posts, this car gets used for daily traffic creeping in a major city, right?

Is there any chance that this low-speed used has 'gummed up' the engine, and maybe a good old-fashioned Italain tune-up is in order?

I know, I know, revving the heck out of an engine doesn't fix everything, but sometime it helps.....

I'd be inclined to add some MMO to the oil, do a Seafaom treatment throuigh a vacumn line, and then run the wee out of it for a while on the highway.....might make a world of difference!


Yeah, I get little chance to go anyplace a la Italian tuneup. So much of the year is hot and unpleasant, and the roads are worse. I get highway time at least once a week for 12 miles, 24 round trip, but not much chance to hammer on it. That, along with the MMO and Seafoam, might be a good answer (and fun, too!).

 

[rslifkin]

For an easy Italian tuneup, get it good and warm, get it out on the highway, lock out the highest gear, get up to 75 - 80 (if possible) to get the revs up. Run for a couple miles, occasionally letting it coast down to 55 - 60 (builds lots of vacuum), then go WOT back to 80 or so. Do this cycle for a bit (obviously when there's no traffic), and it should blow it out nicely.

 

[Benzadmiral]

The big car's gas mileage is looking good thanks to no A/C use and a diet of 100% gasoline. It's been about 2200 miles since my last OC, and about 500 since I had to add oil. If I get an Oil Level Low message -- which, based on the previous distance, could happen in about 300 miles, 10 days' driving for me -- I'll try some MMO. In the meanwhile I'll try to get out on the open highway for a little "spirited" driving.

 

[addyguy]

Sounds like a plan.....

 

[DC44]

I've been chasing the oil burning situation in my Series II 3800. Burns 1qt per 2k-2200 miles and has close to 172k.We have similar driving styles,6-10 mile city trips(me) one way and the occasional highway trip. When I got it at 108k it burned oil at the rate of 1qt per 1200 miles but passed inspection with low numbers. To me that was unacceptable.So I chased the cause of burn-off. here's a list of things I did since purchasing the car in 2006

PCV valve:2X - did nothing

Valve Stem Seals: changed front side first - burn rate went from 1qt/1200mi to 1qt/1600mi. Changed rear at a later date and burn rate went to 1qt/2k mi

Valve cover gasket: Changed at first valve stem seal change. The stater area is no longer black.O.E. starter was coved in oil, the replacement started is still shiny after 2.5 years So they were in need.

Oil Pan gasket: Waste of $55

UIM and lim gaskets change: lim gaskets where leaking coolant and oil had been wicking up the lim bolts since I can remember. Replaced gaskets and manifold thought this would help. Effect = none,....except my sanity. Also my spark plugs no longer have any deposits on them. Another sign of leaky LIM gaskets are leaking.

I'm pretty sure the rear main seal leaks to some degree and maybe the oil pan gasket or the oil is just wicking around it but it doesn't leak on the ground at all not a drop. Emissions numbers have dropped every year since I had the car to almost nothing this year. I have used synthetics the last three oil changes. Maybe this contributed in some way, I don't know. Maybe the engine gets better with age. Also the 3800 has low tension rings which means it will burn a little oil.

After 4 years of chasing this problem The engine has won and I have lost. I have come to terms that I have done all I could and I will stop worrying about it. I have a low oil light but I never seen it come on I think the sensor is bad.I have tried the italian tue up, synthetic oil, high mileage oil, 10w-40 same results. Interestingly the manual says to use a Thin 10w-30 oil.I just add a qt every 2k now since that seems to be the burn rate and don't think about. I'm adding fresh oil. I'm going to extend my oil change out the 7500 miles(the OLM will go off around 4300 miles), I have P.U. in right now and will mix it with Havoline deposit shield as a top off oil.

With 172k miles if I have to add 1qt of oil every 2 months I just chalk that up to the cost of owning the car.

 

[sciphi]

My 3800 that's seen mostly syn oil the past 3 years has always lost a little over long changes. It seemed to lose the most with 10w30, and the least with thin synthetic 5w30's. I may try a synthetic 5w-20 next winter to see if that helps any.