850 disappearing oil

quote:

Originally posted by 850oilburner:
I have a 96 850 that recently broke 100k miles and have noticed it is burning a quart of oil every two weeks and only a few hundred miles. a friend who works on cars and also owns an 850 looked at it and said he doesn't see it blowing blue or oil smelling exhaust nor is it leaking anywhere. We did just change to synthetics but he says that's not it. says maybe something with valves or rings causing this. he says a ring job or rebuilt engine can be pricey but that there is some oil additive called miracle oil or something that can be added to loosen the rings. he says this can either fix the problem or make it worse. Anyone have an idea about this? any suggestions on what to do? the car is in great shape but i can't see spending a few thousand on it at this stage in the game. Thanks for listening.

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Hmm. That is a lot oil burning, wierd it's not showing in the exhaust. Mine burns a bit of oil too, maybe a liter and a half between oil changes. I'm told the ten valve can burn a little more oil and it is normal. Actually good for the motor. A quart per tank of gas sounds like a problem though. From what I hear stay away from oil additives. Some actually condition the metal in bad ways I'm told. I have tried duralube before I heard this and it really didn't seem to do anything at as far as I can tell. Also, loosening of the rings sounds like it would contribute to oil burning, not fix the solution. If its rings it would be some blow by, oil getting past the rings into the combustion chamber. Usually this would show in the exhaust color, giving of a blue smoke. You don't have puddles of oil on the ground in the morning do you? That would be an oil leak somewhere. I would look at the motor area carfully and see if you see any blown gaskets or something that shows considerable fluid leakage.
How's the power? Does it run ok?

ok, so is it correct to assume that I can just add a quart every time the oil gets low and this will cause no damage to the engine? Even if this goes on for the next 50,000 miles? The burning oil started as soon as we switched to synthetic. Within two months and 2000 miles after the switch it was down four quarts. Then after three more weeks I added another quart. These five quarts added were all regular oil, not synthetic. It;s been about two more weeks and it's down maybe a half quart or a little less. Should I just switch back to regular oil at the next change and continue to monitor it? The synthetic was the same viscosity, 10W30. Should I switch to 5W30 or 15W40? I see in the manual that 5W30 is ok too. I checked with the dealership and they said it will probably cost between 4000 and 7000 to tear down the engine and fix the problem. If I can just put in a quart of oil every three weeks it will save me a lot of money and I would rather do that. But I don't want to damage the engine. Will this damage the engine? Does massive oil consumption damage an engine if you let it go? Also, if the compression test shows a bad cylinder does that need to be fixed or will it damage the engine? How much would that cost? I have about 2.5 years left of payments and don't want to trade it until it's paid off because I know I will lose money. Do you think I can keep adding oil for another 2.5 years without hurting the engine? I really wanted to keep the car forever because I like it and heard the stories of longetivity with Volvos. I will keep it another ten years if it holds up but I will trade if the engine is bad. What do you all think?

First off, I wouldn't mix synthetic with regular oil. You can get a nasty seperation leaving parts not properly lubricated. If I were you I would flush the oil and switch back to regular oil, especially with the burn. Synthetic would get very expensive to top up and 850's don't seem to be bother by regular oil as long as it is a quality grade. (in fact in the manual you will see Volvo recommends "energy conserving oils" vs. performance oils) Try to use the same brand and viscosity every service unless you live in a climate that goes to cold winter to hot summer like were I live. The viscosity of the oil you use is related to the outside tempuratures because of the temperature of the oil on start-up and the cooling properties outside temperature will have when at operating tempurature. So, this said the thinner oil (eg. 5W/30) is a cold weather oil. It breaks down easier at high temperatures but remains a very good lubricant in colder climates, the thicker stuff can get a bit gummy. A high temperature oil (eg. 15W/40) is an exeptional oil in very hot weather or if your engine is running hotter than the normal motor (such as hotter plugs, mods, etc.)
This is what I recommend and use all year long. Non-synthetic SAE 10W/30. It can handle cold tempuratures down to -20C (-4F) and stabile outside tempurature to +40C (+104F). If you live in a hotter area than this use SAE 15W/40. Colder use SAE 5W/40 (has a better hot range than 5W/30).

Well it sounds like you are using 10W/30 which sounds right. After you flush the synthetic(mix, yikes!) and put in a good grade 10W/30 back in, run it a bit and do a compression test (engine should be at operating temperature for an accurate read).
A compression test should be inexpensive and give a result if one or more cylinders are damaged. At least you'll know. You may even know someone you can borrow a compression tester from. It looks like a pressure guage with a cord to an end that screws into where the spark plug is. Turn over the engine a few times (hot) with it in and you can read the cylinder pressure on the guage. As easy as that.
I also suspect that maybe the synthetic switch may be the culprate to the whole problem, especially mixed with old oil.
Definatley try switching back and see if the burn continues (with a full flush).
Adding oil constantly will not harm the motor, only if the oil gets low (keep it readable on the dip stick at all times!!!). As long as it is burning though I would change the oil more frequently as recommended because burned oil deposites that have lost there lubricating properties will be left behind in circulation in the motor.

Let us know how it goes, what problems and solutions you come across.

-Spearzy

Just to let you know that the reason why Mobil 1 and other synthetics lubricate better than mineral based engine oil is because it is molecularly smaller than regular oil. This is most likely why you have some oil consumption. We see this at the shop every now and then... a "god" car starts random leaks and oil burning after the customer opted to spend more money and use synthetic oil. We generally don't reccomend syn. oil fot older engines for this reason. Rings going in 100k on an 850? Possible, but not likely. Before tearing into the engine for a rebuild, try first to flush out the syn. oil and go back to mineral based. All manufacturers seem to have a general "one quart of oil over 1,000 miles is acceptable/ within spec" line to appease owners, generally it's more of a mystery of where does it go than harmful. Also be wary of a rear main seal going in the car, this is common in 850's at 100k. Sometimes not easily diagnosed if the car was grimy and dirty underneath and you doa lot of highway driving... spreads the oil thinly across the underside of the car. Keep us posted on your car.... JOE