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Discussion Starter · #1 ·
Hey all,

Very new to owning an E46 so I had some questions. I checked my oil not too long ago (just a few days or so) and the level was fine so I was a little worried when my oil level sensor light came on when I turned my car off in a parking lot at school today. Even though I know that my oil sensor is broken, I immediately checked the dipstick and the oil level was below the middle "safe" portion of the dipstick. I went to class for a few hours and came back and checked again but the level was back to normal in the middle section of the dipstick. Thinking that I was in the clear, I then made a drive to my grandparents house about 20 miles away. I checked the oil level again and it was back to being too low, below the middle section of the dipstick. I was at the house for about 2 hours and when I was about to leave I decided to check the level again. It went back to the middle of the dipstick yet again. However, not wanting to risk driving another 20 miles on what may or may not be low oil level, I went to the gas station around the corner (about 2 mins away) and got some oil. During the drive to the station, the engine got fully warm so I decided to check the level once again just to see what it would be. Below the middle once again. I waited about 5-10 mins and checked again. Still low. So I topped off the oil and began to drive home. On the drive I noticed that the car seemed to run a lot smoother making me think that I have been running on low oil for a while and just not realizing it thus possibly doing damage to my engine during that time. Does anybody know what could be going on here? If I have been running on relatively low oil for a few days, how much damage could I be doing to my engine? Should I be worried? Sorry for the long read but any help and insight would be much appreciated.
 

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As long as you can see some oil on the dipstick when you check properly, you aren't doing damage with normal driving on moderate terrain. You need the proper level for sustained high-G turns and steep hills.

While the engine is running the CCV system pulls a mild vacuum on the crankcase. If your dipstick o-rings seal properly, oil is pulled up the dipstick tube when you turn the engine off oil and the vacuum is released. If you don't see the dipstick plastic section fully covered in oil at the pre-measurement wipe-off, replace the dipstick o-rings and fix any other CCV system leaks.

I suspect that you are seeing a different problem. The engine oil system has many check valves. These keep the oil from draining back into the pan when the engine is off. If these leak it takes a few extra seconds for oil pressure to build during engine start. Some of these check valves are really difficult to inspect, such as the one that requires removing the head. But the most common leaks are in the oil filter housing and they are easy to inspect and fix.

The oil filter cap has a projection at the bottom with two small o-rings. The projection plugs a drain to the oil pan that opens as you unscrew the cap. A long time ago those two o-rings were included with every filter kit. Now you need to buy them separately. The part number is 11427549573, and they are 7x2.5, 7mm ID, 12mm OD. They should be under $1 for the pair and take about a minute to change.

The oil can also leak back from a bad oil filter housing seal. This is a very common external oil leak point, but a failing seal will leak internally as well. If you don't know when it was last changed (do you have service records?), put it on the medium-term project list. Or the near-term list if you have any oil drips. The gasket is under $5, but this is a 2 hour project.

While the oil filter housing is off, inspect the check valve there. These don't commonly fail, but it happens. If the check valve has grooves you can replace the whole oil filter housing, or buy a $50 aftermarket check valve.
 

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2016 M235i 6-spd
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Make sure you check oil on level ground...and at least a few minutes after shutdown. But, overnight, I always get an extra 1/2 qt. registering on the dipstick.

I'd suspect that maybe you were parked on uneven ground and that would affect the reading...and possibly trigger the oil level sensor--I've had that happen when I was a little low and on a hill.
 

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As long as you can see some oil on the dipstick when you check properly, you aren't doing damage with normal driving on moderate terrain. You need the proper level for sustained high-G turns and steep hills.

While the engine is running the CCV system pulls a mild vacuum on the crankcase. If your dipstick o-rings seal properly, oil is pulled up the dipstick tube when you turn the engine off oil and the vacuum is released. If you don't see the dipstick plastic section fully covered in oil at the pre-measurement wipe-off, replace the dipstick o-rings and fix any other CCV system leaks.

I suspect that you are seeing a different problem. The engine oil system has many check valves. These keep the oil from draining back into the pan when the engine is off. If these leak it takes a few extra seconds for oil pressure to build during engine start. Some of these check valves are really difficult to inspect, such as the one that requires removing the head. But the most common leaks are in the oil filter housing and they are easy to inspect and fix.

The oil filter cap has a projection at the bottom with two small o-rings. The projection plugs a drain to the oil pan that opens as you unscrew the cap. A long time ago those two o-rings were included with every filter kit. Now you need to buy them separately. The part number is 11427549573, and they are 7x2.5, 7mm ID, 12mm OD. They should be under $1 for the pair and take about a minute to change.

The oil can also leak back from a bad oil filter housing seal. This is a very common external oil leak point, but a failing seal will leak internally as well. If you don't know when it was last changed (do you have service records?), put it on the medium-term project list. Or the near-term list if you have any oil drips. The gasket is under $5, but this is a 2 hour project.

While the oil filter housing is off, inspect the check valve there. These don't commonly fail, but it happens. If the check valve has grooves you can replace the whole oil filter housing, or buy a $50 aftermarket check valve.
You should only ever check your oil level when the engine is cold and the engine has been switched off long enough for the oil in the top of teh engind (the filter housing and head) to drain back down into the sump at the bottom of the engine. That's when you get a true reading of how much oil you have. If you check the oil then (and on a level surface) the oil level should be between the max and min lines on teh dip stick. Next time you check the oil do it like that. Then replace the dipstick, turn the engine on and let it run for a few minutes then turn it off and chweck the oil agin, You will see the difference it makes. Also, be aware that you can overfill with oil. The maximum is just as important as the minimum. If you exceed the maximum you can start bursting gaskets and you don't want to have to deal with that if you can avoid it.
 

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This is the oil level checking procedure in the owners manual:

Checking the oil level
1. Park the vehicle on a level surface
2. Switch the engine off after it has
reached normal operating temperature
3. After approx. 5 minutes, pull the dipstick
out and wipe it off with a clean
lint-free cloth, paper towel, or similar
material
4. Carefully push the dipstick all the
way into the guide tube and pull it
out again
5. The oil level should be between the
two marks on the dipstick.

The reason most manufacturers want the oil checked warm is because oil, like most other liquids will expand when it warms up. Checking the oil warm take the temperature variation out of chances in the level due to expansion/contraction.

Same theory is used when checking automatic transmission fluid.
 

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You should only ever check your oil level when the engine is cold and the engine has been switched off long enough for the oil in the top of teh engind (the filter housing and head) to drain back down into the sump at the bottom of the engine. That's when you get a true reading of how much oil you have. If you check the oil then (and on a level surface) the oil level should be between the max and min lines on teh dip stick. Next time you check the oil do it like that. Then replace the dipstick, turn the engine on and let it run for a few minutes then turn it off and chweck the oil agin, You will see the difference it makes. Also, be aware that you can overfill with oil. The maximum is just as important as the minimum. If you exceed the maximum you can start bursting gaskets and you don't want to have to deal with that if you can avoid it.
Oil filter housing should be full of oil and NOT drain until the cap is loosened. The check valve and small o-rings at the end mentioned earlier prevent it. The engine will run unnecessarily long without oil pressure every time you start it. Like you said oil still needs to drain down from the head ect but the filter should not drain until it's opened.

Sent from my SAMSUNG-SM-G870A using Tapatalk
 

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Hey all,

Very new to owning an E46 so I had some questions. I checked my oil not too long ago (just a few days or so) and the level was fine so I was a little worried when my oil level sensor light came on when I turned my car off in a parking lot at school today. Even though I know that my oil sensor is broken, I immediately checked the dipstick and the oil level was below the middle "safe" portion of the dipstick. I went to class for a few hours and came back and checked again but the level was back to normal in the middle section of the dipstick. Thinking that I was in the clear, I then made a drive to my grandparents house about 20 miles away. I checked the oil level again and it was back to being too low, below the middle section of the dipstick. I was at the house for about 2 hours and when I was about to leave I decided to check the level again. It went back to the middle of the dipstick yet again. However, not wanting to risk driving another 20 miles on what may or may not be low oil level, I went to the gas station around the corner (about 2 mins away) and got some oil. During the drive to the station, the engine got fully warm so I decided to check the level once again just to see what it would be. Below the middle once again. I waited about 5-10 mins and checked again. Still low. So I topped off the oil and began to drive home. On the drive I noticed that the car seemed to run a lot smoother making me think that I have been running on low oil for a while and just not realizing it thus possibly doing damage to my engine during that time. Does anybody know what could be going on here? If I have been running on relatively low oil for a few days, how much damage could I be doing to my engine? Should I be worried? Sorry for the long read but any help and insight would be much appreciated.
Difference between cold and normal working temperature is about 1/8th inch on the dipstick with a 6.5 litre sump capacity. Not so much to cause concern in my opinion. I prefer to check it cold when the oil is at its least volumetrically speaking.
 

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Discussion Starter · #8 ·
Thank you for all of the information guys! It's all been very helpful. Based on the instructions in the owners manual, I definitely checked the oil level correctly at least a few times such as when I made that trip to the gas station. I made sure to put it on a level surface and waited about 10 mins before checking the dipstick. So I guess my question now is if you guys think I have done any damage at all to my engine? When checking the dipstick about 5-10 mins after operation the level was about a millimeter or so below the very top of the bottom section of the dipstick. Is this level alright to drive at for few days? I feel as if BMW would have made the dipstick in such a way that when the oil level reads low on the dipstick, it is actually at a decently operable level, but just serves as an indication to the owner that the oil level should be raised just to be safe. But then again, like I said when I added some oil to the engine I noticed a difference in the "smoothness" of the drive. What do you guys think?
 

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As long as you can see some oil on the dipstick when you check properly, you aren't doing damage with normal driving on moderate terrain. You need the proper level for sustained high-G turns and steep hills.

While the engine is running the CCV system pulls a mild vacuum on the crankcase. If your dipstick o-rings seal properly, oil is pulled up the dipstick tube when you turn the engine off oil and the vacuum is released. If you don't see the dipstick plastic section fully covered in oil at the pre-measurement wipe-off, replace the dipstick o-rings and fix any other CCV system leaks.

I suspect that you are seeing a different problem. The engine oil system has many check valves. These keep the oil from draining back into the pan when the engine is off. If these leak it takes a few extra seconds for oil pressure to build during engine start. Some of these check valves are really difficult to inspect, such as the one that requires removing the head. But the most common leaks are in the oil filter housing and they are easy to inspect and fix.

The oil filter cap has a projection at the bottom with two small o-rings. The projection plugs a drain to the oil pan that opens as you unscrew the cap. A long time ago those two o-rings were included with every filter kit. Now you need to buy them separately. The part number is 11427549573, and they are 7x2.5, 7mm ID, 12mm OD. They should be under $1 for the pair and take about a minute to change.

The oil can also leak back from a bad oil filter housing seal. This is a very common external oil leak point, but a failing seal will leak internally as well. If you don't know when it was last changed (do you have service records?), put it on the medium-term project list. Or the near-term list if you have any oil drips. The gasket is under $5, but this is a 2 hour project.

While the oil filter housing is off, inspect the check valve there. These don't commonly fail, but it happens. If the check valve has grooves you can replace the whole oil filter housing, or buy a $50 aftermarket check valve.
Have an aftermarket source you can recommend?
 

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You should only ever check your oil level when the engine is cold and the engine has been switched off long enough for the oil in the top of teh engind (the filter housing and head) to drain back down into the sump at the bottom of the engine.
My point above is that the oil in the filter housing *should not* drain back into the pan. If the oil does leak past the seal or check valve it will read between 1/2 and 1 quart higher.

It's perfectly OK to check the oil when the engine has just been shut off. Just keep it in mind that it may read a little high because of thermal expansion. The minor difference shouldn't matter. If you are close to the low line, add a quart/liter. If the oil is a little higher than the high line, it's not a problem.

Remember that the low and max marks are for operation over all conditions with plenty of margin. If you don't drive on steep hills or long sweeping high speed turns you can overfill or underfill without issue. People that do track days often overfill because oil starvation is a much more immediate problem than frothing the oil from the crank splashing in the oil pan.
 

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I've had my e46 a year now and I am still trying to figure out my dipstick, still trying to figure out whether it's better to err on the side of an overfill or an underfill.

I just wanted to point out that if the oil level reads midway between min and max on the dipstick, that is supposed to indicate that you are about a 1/2 quart short on oil - which is safe. And when the orange/yellow oil light comes on after shutdown, that is supposed to indicate that you are about a 1/2 quart, or more, short on oil - it's a friendly warning that while you have enough oil in engine - your oil is getting low and you should top off if/when it is convenient.

Mine also runs more smoothly immediately after I add oil, which makes me wonder if I should be more gung ho about topping off my oil.
 

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And when the orange/yellow oil light comes on after shutdown, that is supposed to indicate that you are about a 1/2 quart, or more, short on oil
This can depend on the car. 7 qts of oil in my 330i and the level is right between the 2 marks but most dealerships will say it is underfilled by a half qt. I never worried about it and just filled it to the half way point between the marks.
 
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