[Tmaccus]

Hey Guys,

Here's a quick rundown of the symptoms and what I've done on my 06 325:
1) Oil level was constantly at "low" even after pouring in 1Q of oil.
2) I replaced the oil sensor. When replacing the oil and oil sensor, I noticed that only 2Q of old oil came out of the engine. The oil was really thick and fouled up. The oil filter was also really fouled up.
3) After the oil and sensor repacement, the new sensor was giving the "ok" full level after the oil and sensor repacement.
4) Oil would gradually go down 1/4Q every week. I can see it going to after week 2: 3/4, then 1/2 after week 3, then 1/4 after week 4.
5) But here's the real mystery: 1 month later, the new sensor is doing the same thing as the old sensor and the level is stuck on "low" or 1/4 level immediately after adding 1Q.

What do you guys think is going on? I have over 280K mi on car and do regular oil changes. I use OEM everything. The car is running strong otherwise. I don't notice any smoke or smell.

Thanks for your help.

[OP3NAIR]

If the new sensor says the same thing as the old sensor, then I venture to think the sensor isnt broken. With that many miles, start looking for an oil leak. Sounds like its large enough to find it fairly easily.
If not, do a leakdown test on the cylinders and make sure the rings are sealing. You could also be leaking through worn valve guides and seals.
Alternative option: after 280K, declare victory, get another one.

[PhaseP]

I noticed that only 2Q of old oil came out of the engine

Logical conclusion would be you are either burning or leaking oil fast.
Engine takes 7 qts of oil.

[The0pportunist]

280,000 miles? I am very impressed.
German engineering for the win.

[ThatRWD]

The oil sensors are known to not work correctly after you get to 180k, it's a software issue, not a sensor issue.

http://www.e90post.com/forums/showthread.php?t=926864

Best thing to do is empty out the oil, put in 7 quarts of new oil. Drive for 2-5 minutes to get the oil circulated, then drain & measure how much comes out. Should be pretty close to 7 quarts, if not exactly. Put in new oil, drive for 3000-5000-7000 miles or however much you think you can last without burning over a quart. Test and evaluate, you should now know at what rate your car burns oil. Driving styles & oil types will affect burn rate between oil change intervals (mobil1 is known to burn faster than BMW Castrol).

[shadow191]

But that's for the oil life, not oil level.

If OP only got 2 quarts out at the last oil change, seems the sensor is working if it says low oil. I'd say change the oil again and see how much comes out this time. If it's low again, that's not a sensor issue.

[ThatRWD]

Pretty sure it's for both.

[paco89]

I once had an issue with my sensor after replacing valve cover gasket and oil pan gasket. Then did an oil change...after driving for a couple of days it started reading low all the sudden, i got concerned and added 1qt to it but did nothing to the reading stayed as low. After i got home i drained the oil and it was overfilled by 1qt....meaning the sensor was failing. I refilled the engine with the 7qts and kept driving for a couple of days before i ordered a replacement sensor. ALL OF THE SUDDEN...the sensor worked again and read half full for a while then after driving even more, it read OK as full...ever since it has read fine...so it seems that it took time to adjust itself, im talking days... so i cancelled my previous order on the replacement sensor...just a thought.

[AllBlackBimmer]

Check your valve cover, oil filter housing, and pan gasket for leaking...

Apparently there is an issue with the oil sensor after like 180,000 mile or something like that.

There is a member on here that makes regular post about his high mileage e90 and his oil sensor problems.

Apparently its a fault in the CPU, and even BMW could not "reset" it.

[msjt]

2 qts?!! Holy shit. How did you lose almost 5qts of oil and not notice any puddles?

[Tmaccus]

OP here. There are no leaks. My driveway is clean as a whistle. I still can't believe the car survived on 2 quarts for an extended period of time.

[turo]

When you rev the car, is there smoke coming out of the exhaust? If there is blue/gray smoke, that traditionally means that your engine is burning oil, which is typically (but not necessarily) caused by worn down piston rings, which would be VERY likely with such a high-mileage engine such as yours.

[Tmaccus]

Originally Posted by turo

When you rev the car, is there smoke coming out of the exhaust? If there is blue/gray smoke, that traditionally means that your engine is burning oil, which is typically (but not necessarily) caused by worn down piston rings, which would be VERY likely with such a high-mileage engine such as yours.

No smoke from the tail pipes, just from the tires... Joking. Anyway, no smoke at all. The car runs smooth as silk.

[shadow191]

Nothing on the belly pan/splash shield? That usually keeps oil off the driveway, but I don't think it would hold 5 quarts either.

Originally Posted by Tmaccus

OP here. There are no leaks. My driveway is clean as a whistle. I still can't believe the car survived on 2 quarts for an extended period of time.

[lichtgelb]

Have the CCV and associated hoses been replaced? It's under the intake manifold towards the firewall on the 06 325.

[Tmaccus]

Originally Posted by lichtgelb

Have the CCV and associated hoses been replaced? It's under the intake manifold towards the firewall on the 06 325.

I got my starter replaced at the dealership about 8 months ago. Do you know if they would touch the components you're refering to?

[lichtgelb]

Originally Posted by Tmaccus

I got my starter replaced at the dealership about 8 months ago. Do you know if they would touch the components you're refering to?

It's attached to the manifold so it would have to come off with it to gain access to the starter. If the CCV is allowing oil to go into the intake and not return to the sump then you would burn off oil. You would have to pull the throttle body to see if there is any oil residue in the intake to know for sure. Normally it will return combustion vapors to the intake to be burnt and allow oil to drain back to the oil pan. There are several failure modes for this and excessive oil usage is one of them.

[Tmaccus]

Originally Posted by lichtgelb

It's attached to the manifold so it would have to come off with it to gain access to the starter. If the CCV is allowing oil to go into the intake and not return to the sump then you would burn off oil. You would have to pull the throttle body to see if there is any oil residue in the intake to know for sure. Normally it will return combustion vapors to the intake to be burnt and allow oil to drain back to the oil pan. There are several failure modes for this and excessive oil usage is one of them.

The oil level was at 1/4 for about a week then I added some oil. But the level is still stuck at 1/4 for a couple of days now.

[lichtgelb]

Originally Posted by Tmaccus

The oil level was at 1/4 for about a week then I added some oil. But the level is still stuck at 1/4 for a couple of days now.

The lack of a dipstick on these cars is annoying. I'm rebuilding an 06 325 that I bought at a salvage auction with front end damage. When I went to drain the oil about 13 quarts came out. I have no idea what the story was behind that. The oil pan and valve cover gasket leaked so I strongly suspect the CCV is bad so my weekend project is removing the intake. I have a feeling the previous owner was dumping oil in there to compensate for the leak and perhaps it was burning though the intake as well. So I'm replacing the CCV and hoses due to the other signs and also as PM since I'm rebuilding so much of the car anyway.