A new way to manage oil levels on track

[fe1rx]

BMW would like us to keep our oil level between about 5.0 liters and 6.5 liters and they would like us not to obsess about the exact level. They would prefer that we didn’t exceed 6.5 liters. To this end my ’08 135i and my ’11 328i both incorporated similar oil level display logic. An acceptable oil level was shown with a bar graph showing the oil level mid-way between min and max hash marks with the text “OK”. In the consumer’s brain this looks like half a liter down from full and “OK” is not a glowing endorsement. Wouldn’t full be better? Those who harbour such thoughts will top their oil up until it eventually tells them it is overfilled.

Somewhere along the way BMW updated the display logic and now it shows “OK” with a full bar graph if the oil level is acceptable, “+1” if it needs a liter to stay within the preferred range, and exceeding 6.5 liters doesn’t produce an overfilled indication. The full bar graph works well for those with OCD.



This system doesn’t work well at the track, where both the N54 and N55 struggle with low pressure transients if the oil isn’t actually full (6.5 liters) or slightly above. The problem is that the oil level management system will never tell us when the oil level is actually full. Unless we have just changed our oil and accurately measured the amount added, we never actually know the oil level. This was brought home to me a while back when I experienced a 4 psi low-pressure transient on track. Typically I see the oil pressure become unstable at 1.0 g with transients as low as 20 psi, but in this case the transient started earlier and went alarmingly lower. Luckily, I was monitoring engine health data on my first session and noted it.



Adding half a liter of oil resolved the problem, but of course the oil level indicator showed “OK” both before and after the addition. I added another half liter just to see if the indicator was working, expecting an overfull indication, but as I discovered the system didn’t show that.

To understand the system, I did some experimenting back at the shop:

4 liters is 2.5 liters low, but is “+1”:



6.5 liters is nominally full and shows as full and “OK”:



8.0 liters is 1.5 liters over full, but also shows as full and “OK”:



My practice is to add 7.0 liters when changing oil on my track car, with the intent of maintaining the oil level between 6.5 and 7.0 liters.

As it happens, the oil level sensor does actually measure the oil level (height in mm) in the oil sump, and this can be viewed as live data with a code reader. I have used both PROTOOL and a Foxwell NT510 for the purpose. A generic OBDII scanner without BMW-specific software won’t work.

Wanting to a) see if my sensor was actually working properly, and b) understand the relationship between the height reading and the oil volume, I undertook a calibration of the sensor by adding oil in increments and taking height readings at each volume.



From this I was able to divine the oil level management system logic, but more importantly to discover that live data provides me with a real functioning “dipstick”. The sensor maxes out at 74 mm which corresponds to about 6.8 liters (or above). Any reading above 70mm satisfies my desired oil level, and the calibration curve suggests the following oil fill logic:

[spidertri]

This is really good info. I'm going to have to start up protool and find the readout for this because it will be incredibly useful at the track.

On my 128i, I do not get an accurate oil level reading throughout the track day. Usually I have to drive the car at normal speeds for around 20 minutes before the oil level will update and show that I have less oil than expected.

Does the live reading react quickly to changes in the oil level?

Have you ever changed your oil level sensor? I'm wondering if mine is old and not performing as well as it should be.

[fe1rx]

Reading the live oil level requires connecting an appropriate code reader to the OBDII port, then configuring the reader to display the Engine Oil Level parameter. A valid reading requires the same warmup procedure as using the bar graph on the dash. In fact, I just wait until the bar graph shows up and then I read the level on the code reader at that time. If you read the level immediately after starting the car it will start at 74 and then gradually count down to the actual reading as the engine warms up.

I find connecting with my Foxwell NT510 scanner to be a bit more convenient than using PROTOOL simply because it is powered from the OBDII port and I don’t have to bother with Android, or a charged device. Connecting with the NT510 requires the following steps:

1) Connect scanner to OBDII port
2) Select BMW (your reader needs to have BMW-specific software installed)
3) Start a new BMW session
4) Select “1 Automatic selection”
5) Select “2 Control units”
6) Select “1 Drive”
7) Select “5 Engine-DME Digital Motor Electronics”
8) Select “6 Live data”
9) Select “1 Motor operating values”
10) Select “Engine oil level”
11) Select “View Data”

The engine oil level is displayed in mm (no decimal places). There is another oil level parameter called “Engine oil fill level, briefly” which can be displayed but it is equivalent to the dash bar graph, so not useful.

Connecting with PROTOOL is a bit more complicated because it can display vastly more live data channels so finding the right one takes a bit more time (and I find getting it to recognize the vehicle sometimes takes a couple of tries). In PROTOOL the channel is called “Oil Level Sensor”. There is another one called “Level of Engine Oil”, but it is a numeric value associated with the bar graph and is not useful. PROTOOL displays the oil level in mm with 1 decimal place precision, which is interesting, but ultimately no more useful.

[fe1rx]

Originally Posted by spidertri

Does the live reading react quickly to changes in the oil level?

Have you ever changed your oil level sensor? I'm wondering if mine is old and not performing as well as it should be.

After you add oil, you will need to shut down for about 5 minutes, then restart the car and go through the dash oil level measuring process before you get a stable reading.

Track driving is too dynamic to get a stable oil level. I suspect that is why it is not giving you a reading after being on track. Under normal driving, once the car is warmed up the dash will give you a reading immediately on request because the sensor has been seeing a stable valid reading for a while.

I doubted my sensor too, but the things are pricey and apparently often changed unnecessarily so I wanted to investigate first. Also, I cleaned mine ultrasonically before I went through the process. Nothing indicated it was excessively dirty or clogged up.

I suggest at your next oil change you try the code reader at a couple of known oil levels to see if they agree with my findings. If they do, your probe should be good.

[Brian_]

Glad I've been procrastinating changing my oil after my last few track days, now I can grab some good baseline readings at a few fill levels and hopefully stop trying to use that little bar graph.

[spidertri]

Yeah I got it set up in Protool pretty easily and was logging my oil level on the drive this morning.

The sensor does react very quickly, fast enough to see the level change going uphill or downhill. It would be cool to see if one of the other parameters shows the "average" reading that gets reported as the bar graph.

I'm dropping my oil pan this winter to install a baffle, I'm trying to think if there's any tests I can do with the pan off to better correlate the level.

[Alow]

this is going to be extremely useful. i’ve been wondering about this at the track. i always add an extra 0.5 but can never tell when I need to add more again because the dash always says “Ok”. Thank you for sharing!

[amg6975]

Originally Posted by spidertri

It would be cool to see if one of the other parameters shows the "average" reading that gets reported as the bar graph.

The DME does not send out any sort of reading. It just sends out which one of the 5 fixed display options the Kombi should display. Which is not particularly helpful.

[houtan]

Thanks for this. I am going to try this with my n55 using a foxwell 510.

Side question, fe1rx , are you using anything to prevent oil starvation (baffle, accusump, etc)?

[fe1rx]

Originally Posted by houtan

Side question, fe1rx , are you using anything to prevent oil starvation (baffle, accusump, etc)?

At the moment, I am just making sure the oil is slightly over full and keeping an eye on the pressure transients.

After that 4 psi transient though, I am seriously contemplating an accusump. Given that I have an oil pressure transducer and a dash logger capable of controlling a solenoid valve, I would use the dash to control the accusump valve. I have been experimenting with control logic and observing when it would open the valve to keep myself entertained. The dash can consider any number of parameters. For example, open the valve a) when cranking, or b) when a specific steering wheel button is pushed, or c) when rpm is greater than 2500 and oil pressure is less than 60 psi.

[Piper1]

From Zpost for anyone with N52. Thinking of going this route in the not too distant future. You’ve got a spot to add an actual dipstick!

https://www.zpost.com/forums/showthread.php?t=1859868

[spidertri]

The late stamped steel pan on manual transmission cars doesn't have that port unfortunately.

I think early cars have a tube there for the PCV drain.

[rismo]

The fancy way of me just overfilling my engine by purpose when tracking.
Will Definity add this to my track pony, thx.

[houtan]

Was finally able to try out the oil level measurement using my NT510. I was around 72mm which means I was properly overfilled for my last track day. Pure luck but it makes sense why my oil pressure was good the entire day.

I also learned that the nt510 can code and do a bunch of other things as well. Really cool. Thanks again for the info.

[spidertri]

Changed the oil over the weekend and I can confirm on the N51 that adding 7.0L of oil results in a measurement of 73mm from the data.

[houtan]

Originally Posted by spidertri

Changed the oil over the weekend and I can confirm on the N51 that adding 7.0L of oil results in a measurement of 73mm from the data.

I put in 6quatrs and was at a little more than 73mm. Since you were able to get seven, I went back and checked today with the OBD scanner. I’m still at the same value, but I wonder why you were able to get seven and I only need six quarts. Does the N 52 have a larger oil capacity?

[spidertri]

N52 capacity is 6.5L, I went to 7.0L to be overfull for track days.

I had my oil pan off to install a baffle so it drained for several days and the pan was completely emptied.

[rackhenry]

Thank you for the great writeup! Thinking of getting a Foxwell scanner as well and this is one purpose I was not aware it was usable for!

[JohnDaviz]

Thank you for this valuable information!!

I went ahead and asked for logging Oil Level with MHD. It works great! You can check all information here:
https://*********************/thread...9/#post-133992