[NxTH]

335i N55 2013,

2 days ago I decided to check my oil level. It was at the minimum mark, and told me to add 1 quart. So I added about half first, went for a drive and came back. Measured the level and it was in the right in the middle. I added almost all of the rest, but left a bit in the quart bottle.

Next day, went for a drive and came back, did a new reading. It's still reading the oil right in the middle so nothing changed. Added the rest of the quart I had in the bottle, went for a drive, still in the middle.

Does it take a few days to update, or is the sensor bad?

[Eschmacher]

It's not an exact measurement. If it's showing in the middle, then you're fine.
Also, the sensor is touchy to the angle of the vehicle, so even doing a measurement in one location and moving to another at a different angle can change the result.

[NxTH]

Originally Posted by Eschmacher

It's not an exact measurement. If it's showing in the middle, then you're fine.
Also, the sensor is touchy to the angle of the vehicle, so even doing a measurement in one location and moving to another at a different angle can change the result.

I get that. Though, what I don't understand is how it works. People seem to say that the difference between minimum and maximum is 1 liter or quart.

1. iDrive says minimum, add 1L.
2. I add half a litre -> idrive shows middle
3. I add most of the other half -> idrive shows middle
4. I add the rest -> idrive shows middle

Why did it update once, and never again? What's the point of the whole system if I can't check the level reliably? Why does it update the first half, but not the second?

[thejeremyman9]

As noted above, its mostly qualitative, semi-quantitative. Next time you change the oil, check using idrive before draining, measure how much you drain, and add more accordingly.

[visionaut]

From this description (sry left pics out), it seems:

1) the Qualitative measurement is: greater than min OR less than max = okay (lol)
2) bouncing ultrasonic pulses off a moving liquid surface isn’t as good as reading a graded stick. Chassis levelness and oil age/viscosity/temp caveats are funny.
3) there’s a whole 1 liter RANGE to OK…

=======

Functional description
The oil level sensor is attached to the oil sump and is accessible from below. There is no longer an oil dipstick on vehicles with an oil level sensor. These engines have an electronic oil level check. The concept for the display is also new (see Owner's Handbook).
The oil level sensor consists of the evaluation electronics and a measuring tube. There is engine oil in the measuring tube.
dependent on the motorisation: In addition, a signal for the engine oil temperature is supplied.

Item Explanation Item Explanation
1 Measuring tube 2 Oil-level sensor
3 three‐pin plug connection
The evaluation electronics transmit ultrasonic pulses. These ultrasonic pulses are reflected at the transition point from oil to air (echo impulse). The evaluation electronics receive and amplify these echo impulses. The amplified echo pulses are then converted into a digital signal.

The distance travelled by the sound wave determines the echo lag time. The evaluation electronics calculate the oil level on the basis of the echo lag time.

Changes in the engine oil (e. g. ageing or infiltration in the engine oil) and the engine oil temperature influence the signal propagation delay. For this reason compensation is effected in the oil level sensor.

The signals are transmitted to the engine control as pulse-width-modulated signals.
Display and operating concept for the electronic oil-level check
The engine oil level check with the oil level sensor is coupled with a change to the display and operating concept.

Qualitative measurement while driving
* Status display (oil level OK OR oil level at minimum OR oil level below minimum)
* Display available at all times
* Warning by means of Check Control message from oil level at minimum


Item Explanation Item Explanation
1 Vehicle status 2 Engine oil level OK
3 Engine oil level at minimum. Please top up with one litre of engine oil. 4 Engine oil level below minimum. Please top up immediately with one litre of engine oil.

Quantitative measurement during vehicle standstill
* Driver must actively request measurement
* Measurement only possible under defined marginal conditions
* Time: approx. 1 minute


Item Explanation Item Explanation
1 Vehicle status 2 Measurement only when stationary with idle engine at operating temperature and when vehicle is on level ground. Do not operate the clutch or gas.
3 Conduct detailed measurement 4 Detailed measurement in progress.
5 Engine oil level OK. (I.e. above min and below max)

Quantitative measurement during vehicle standstill using the example of the radio
(Huh? I think mean the diagnostic menu in the instrument cluster.. based on the pic)

Item Explanation Item Explanation
1 Oil level OK! Conduct detailed measurement? 2 Yes OR No
3 Detailed measurement is running, progress: 17 % 4 Engine oil level OK.

[NxTH]

Originally Posted by visionaut

From this description (sry left pics out), it seems:

1) the Qualitative measurement is: greater than min OR less than max = okay (lol)
2) bouncing ultrasonic pulses off a moving liquid surface isn’t as good as reading a graded stick. Chassis levelness and oil age/viscosity/temp caveats are funny.
3) there’s a whole 1 liter RANGE to OK…

=======

Functional description
The oil level sensor is attached to the oil sump and is accessible from below. There is no longer an oil dipstick on vehicles with an oil level sensor. These engines have an electronic oil level check. The concept for the display is also new (see Owner's Handbook).
The oil level sensor consists of the evaluation electronics and a measuring tube. There is engine oil in the measuring tube.
dependent on the motorisation: In addition, a signal for the engine oil temperature is supplied.

Item Explanation Item Explanation
1 Measuring tube 2 Oil-level sensor
3 three‐pin plug connection
The evaluation electronics transmit ultrasonic pulses. These ultrasonic pulses are reflected at the transition point from oil to air (echo impulse). The evaluation electronics receive and amplify these echo impulses. The amplified echo pulses are then converted into a digital signal.

The distance travelled by the sound wave determines the echo lag time. The evaluation electronics calculate the oil level on the basis of the echo lag time.

Changes in the engine oil (e. g. ageing or infiltration in the engine oil) and the engine oil temperature influence the signal propagation delay. For this reason compensation is effected in the oil level sensor.

The signals are transmitted to the engine control as pulse-width-modulated signals.
Display and operating concept for the electronic oil-level check
The engine oil level check with the oil level sensor is coupled with a change to the display and operating concept.

Qualitative measurement while driving
* Status display (oil level OK OR oil level at minimum OR oil level below minimum)
* Display available at all times
* Warning by means of Check Control message from oil level at minimum


Item Explanation Item Explanation
1 Vehicle status 2 Engine oil level OK
3 Engine oil level at minimum. Please top up with one litre of engine oil. 4 Engine oil level below minimum. Please top up immediately with one litre of engine oil.

Quantitative measurement during vehicle standstill
* Driver must actively request measurement
* Measurement only possible under defined marginal conditions
* Time: approx. 1 minute


Item Explanation Item Explanation
1 Vehicle status 2 Measurement only when stationary with idle engine at operating temperature and when vehicle is on level ground. Do not operate the clutch or gas.
3 Conduct detailed measurement 4 Detailed measurement in progress.
5 Engine oil level OK. (I.e. above min and below max)

Quantitative measurement during vehicle standstill using the example of the radio
(Huh? I think mean the diagnostic menu in the instrument cluster.. based on the pic)

Item Explanation Item Explanation
1 Oil level OK! Conduct detailed measurement? 2 Yes OR No
3 Detailed measurement is running, progress: 17 % 4 Engine oil level OK.

Let me guess. There's a whole progress bar with a graphic, but it actually only has 5 spots it can be in?

Above max
Max
Middle
Minimum
Below Minimum

So I could fill up 1L, but if it's missing 100ml from Max, it's going to show Middle. This can result in the consumer accidentally overfilling it as there is no change.

[thejeremyman9]

Originally Posted by Nico-

Let me guess. There's a whole progress bar with a graphic, but it actually only has 5 spots it can be in?

Above max
Max
Middle
Minimum
Below Minimum

So I could fill up 1L, but if it's missing 100ml from Max, it's going to show Middle. This can result in the consumer accidentally overfilling it as there is no change.

I've only ever seen middle and max personally. Ive seen someone post a picture of minimum. Never seen pics of above max or below min, so not sure if they exist.

Also on your 2nd point, not sure how it "rounds" - so if your example would round up to max or round down to middle. The best thing to do is measure on a hot car right before doing an oil change and add accordingly on refill. So if you measure middle before draining oil, on refill add what came out + 0.5L. Then drive the car up to temp, and remeasure after oil change.

[HighlandPete]

Originally Posted by Nico-

Let me guess. There's a whole progress bar with a graphic, but it actually only has 5 spots it can be in?

Above max
Max
Middle
Minimum
Below Minimum

So I could fill up 1L, but if it's missing 100ml from Max, it's going to show Middle. This can result in the consumer accidentally overfilling it as there is no change.

Could be working within tolerance...

I'm not sure if all model screens show the same graphics. For example, diesel's definitely have an overfill "Above Max" level indicator, as they can suffer from oil dilution due to leaking injectors, faulty DPF regenerations.

My F11 N55 shows four level segments between max to min. I can drop a segment and can top off with 250ml and get back to maximum. Have done so several times in my ownership.

[visionaut]

I believe it rounds up if >3/4, towards 1/2, and down if <1/4, within the “OK” range.

There’s below Min (immediate add 1lt), Min (add 1lt), OK (min thru max, averaged per above), Max, and a Code/CEL on the Overfill condition.

So the N55 seems quite flexible in oil fill range. Besides the 1 lt range to “OK”, I believe there’s almost a full liter between Max and the Overfill error. I know of HPDE drivers that readily start almost 0.6 lt over Max without throwing Overfill errors.

I’ve also noted reports of Max right after an oil change/reset than turn out to be 1/4-1/2 lt low after a few days driving for some folks… (not sure why)

It’s also my understanding that 6.5 lt = Full is the directed refill amount for a normal oil & filter change. Yes there’s more oil present (to do an oil consumption weight test, you’re directed to spin the crank hub 360deg to get the rest out of the block, plus there’s residual that’s in the oil cooler). Explains why for a new engine the oil quantity is 8 lt). They tell us 6.5 lt because that’s the oil service quantity (it doesn’t make sense to me they’d have us guessing how much to add or measuring drainage for routine maintenance refills).

Regardless - I’d really prefer a dipstick. (Lol)

I saw the dipstick for the N55 from Garagetistic, but it requires drilling their own aftermarket oil pan to do it…

[HighlandPete]

Mine can show like this, just a 1/4 segment, (from another topic on here, pic by Bmwbreed).

[NxTH]

Strange. Mine is like this after adding 1L from minimum. It never even warned me about low oil, only after I manually checked the level.

[NxTH]

After an oil service and 6.5L total added, it's now showing Max again. So it was probably missing more than 1L..

[thejeremyman9]

Originally Posted by Nico-

After an oil service and 6.5L total added, it's now showing Max again. So it was probably missing more than 1L..

Did you measure how much you drained?

[NxTH]

Originally Posted by thejeremyman9

Did you measure how much you drained?

I use a 3rd party garage since I have a bad back. Didn't think to ask. My guess is it was missing a few drops from max.