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I am in a really weird situation. I have a BMW 325i(2002). I bought it second hand and I have been driving it for 5 years.

Now, lately I have been having to tap my oil every 500 miles with 2 quarts. I did talk to a local mechanic and he said that with age, this happens to all German cars. My point is that still every 500 miles is still a LOT. May be I am wrong and this is very common. However, I want to know how common is it. If not, what are my options. I am pretty sure there is no leak in my car because I never see a single droplet in my drive way.

I am suspecting two possible scenario

  • There is an internal leak where oil is leaking into internal parts and the evaporates.
  • There are chances of extreme oil burning.

Now, This car has 130,000 miles on it and I am not driving it more than 4000 miles a year. I only use it for my commute which is 4.5 miles one way and for little errands. However, My puzzle is that why does it happen? Should I take to to BMW for a comprehensive check? I really am less interested in spending a lot of money on this car since it is really old and am worried that BMW will push for a costly solution. Any ideas on hos to proceed with this issue?

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    Since it is leaking out at 2 quarts every 500 miles (yes, excessive ... very excessive), it has to be going one of three places: leaking; burning; combination of the two. When I say leaking, I'm talking externally, as in out on to the ground. If it was burning that much, you'd definitely be seeing blue exhaust out the back of your vehicle. You may want to run your finger on the inside of the tail pipe and see if there is any oily residue there. Other than that, place a piece of clean cardboard under your engine over night and see if any spots appear on it. – Pᴀᴜʟsᴛᴇʀ2 Mar 3 '15 at 2:18
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    @Paulster2 - about tail pipe - that year vehicle must be equipped with catalytic converter - so all oil is burned by catalytic. Of course it is possible, that catalytic was removed completely. – Guntis Mar 7 '15 at 9:02
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    @Guntis ... Burnt oil will ultimately clog the cat. It starts by coating the catalyst which degrades performance. As performance is degraded, it burns less of the oil hydrocarbons. Vicious cycle. If you can see blue smoke coming out of the tail pipe, the cat is not completely burning the hydrocarbons, just as when you see black smoke coming out, but that is from excessive fuel. – Pᴀᴜʟsᴛᴇʀ2 Mar 7 '15 at 16:21
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The culprit is usually shot piston rings. They act as a buffer between the combustion chamber and the bottom half of the engine. If they go, oil can seep into the combustion chamber and get burned up along with the fuel. To fix this, they'd have to take the entire engine apart to get at the bottom of the pistons. It's not a cheap procedure.

Or maybe you're lucky and it turns out to be an external leak which just requires a new seal put in place.

I found this forum that details the usual places your specific car would spring a leak. Though to be fair, those places are the same on just about all brands.

A leakdown test should tell you whether the cylinder is leaking. An experienced mechanic should also be able to tell from the state of your spark plugs whether something is getting into the chamber that shouldn't. E.g. a dirty plug means oil, a suspiciously clean plug means antifreeze (blown headgasket), a melted plug means a broken fuel injector, etc.

  • is there a test which can precisely tell me if it is shot piston for sure or not? – Lost Mar 3 '15 at 18:14
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    Piston ring, not piston. But yes, a leakdown test should do it. An experienced mechanic should also be able to tell from the state of your spark plugs. – Captain Kenpachi Mar 4 '15 at 7:35
  • Rear main seals also a possibility – Zaid Mar 5 '15 at 11:05

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