DIY: How-to Read the Oil Level via INPA

[RocketyMan]

A resounding pain-point I see on this forum is many people not being able to read their oil level. Whether it be after an oil change, over the road reading, underfilling/overfilling their oil, etc.--it all calls into question getting a "good reading" on what the actual oil level is. Some have even gone to the extravagant level of retrofitting a dipstick to the oil pan. This seems excessive and unnecessary to me, but may-be needed in some racing applications where the stock DME and/or KOMBI is not used.

Successfully, I was able to do some experimenting via INPA and found a DME section where you can see a static reading of the oil level sensor in the sump. I did this with an oil change and measured out exactly 9.5 quarts of added oil after draining everything in the car including the left over bit in the OFH. Do keep in mind that there is roughly 3+ quarts of oil all throughout the oil cooler, galleys, VANOS, pumps, heads, etc. that is left over residually.
From a completely dry-engine/fresh-rebuild and empty oil cooler, I find that the total oil in the system capacity is around 12+ quarts.



Here is BMW's explanation of the Oil Condition Sensor. This is good to understand the concept of digitally evaluating and reading level. Review the attachment I posted on this.
https://www.m3post.com/forums/showpo...0&postcount=33

Remember that oil quality is the measure of excess condensate in the oil--not how "good" or brand your oil is.



The DME uses this sensor via the BSD or LIN data. Keep in mind that there are THREE things the DME uses this bus for: Alternator, IBS, and Oil Condition Sensor. This means that if any one of those items on the BSD bus is "shorted" or malfunctioning, then everything potentially on that bus will be--including the oil level sensor.


Now to read this static level, make sure your car is level on the ground.
How do I know my car is level? - Put a small level gauge in your door jamb where the ///M door sill is to get a good idea.
Then utilize INPA and find the report out.

[RocketyMan]

Next find the "analog" section of INPA and you'll see a section where "Oelniveau [mm]" as an option. This is what the actual sensor is reporting a distance up in mm of the sensor.

In this example, I completely drained the oil in my car to verify this. Thus, 0 [mm] was reported.
NOTICE: the permittivity was reported also as 0 -- this would indicate there is NO OIL in the sump; not safe to start the car. The KOMBI would also report this as "NOT OK" when trying to evaluate the oil before starting the car.

[RocketyMan]

Now verifying this response when filling up the sump with oil, I can see the sensor report increasing values when adding in the last 4 quarts of oil.

KEEP IN MIND, there is a sort of hysteresis on the oil level sensor as you're adding oil. It takes time for the oil to drain down into the sump from the valve cover, thru the head, into the first sump, then overflow into the main sump. Thus, give the oil time and the sensor rebound time.

[RocketyMan]

Here is the reading after letting the vehicle sit a long time so that all the oil would drain into the sump after only 9 quarts of oil.

50 mm would be somewhere around the "minimum" reading for a "full" mark--but keep in my the oil temperature is relatively low. The volume increases as temperature increases.

[RocketyMan]

This shows the oil level of 58 mm with 9.5 quarts of oil in a non-started engine.

[RocketyMan]

Now finally after running the engine and going for a drive here is a static reading after letting the engine sit overnight with 9.5 quarts of oil.

Here we see 55 mm of oil level. This is what I would consider the "FULL" mark on a fresh oil change checking it statically. I consider this to be the goal of a full oil level.

[RocketyMan]

A couple of things to note.
I find that the thicker oil might be harder for the sensor to evaluate as quick. Also, this particular oil level sensor is on the shorter side when compared to other BMW oil level sensors I worked with. Because of this, it limits the granularity of the reading I think in comparison to something like an N52 oil level sensor that is much longer.

Even the BMW TIS explanation explains that viscosity can be challenging to evaluate as well as the age of the oil. Sometimes it just might be better to change your oil more often than the ridiculous 10k/12k mile interval that is suggested. Also, going on short trips can cause issues with reading--this is due to excess water in the oil and not evaporating out. This is why it is so important to get your oil temp up over 100C everytime you drive.


The intent of this DIY is to establish a good way to evaluate if you are having issues with your BSD or not, and to quickly asses a good rough estimate on your oil level. Oil level changes with temperature--and this is accounted for in the evaluation strategy of the Oil Condition Sensor. So keep that in mind.

Lastly, here is a full, HOT level reading after shutdown for around 10-15 minutes. The oil level was still evaluated as "FULL" on the iDrive not being overfilled.