Anyone Know What This Maintenance Reminder Is For?

[JCL]

Originally Posted by ard

JCL- figured this would catch your eye...

I dont think we know really WHAT is being measured by the BMW capactive 'oil quality' sensor. Metal? Viscosity? A combination? I will bet money that it cannot, however, measure 'additive package'. but thats not the topic here.

The odd thing is that I cannot recall ANYONE posting a CBS warning to change transfer case oil, ever....

There have been one or two warnings posted. I think they were all X3 models. No iDrive warning, in that case, but the rest is the same. Not many get the warning because of tendencies to change fluids early and often, over and above manufacturer's recommendations. That's a joke, BTW.

I think we do know what the engine oil sensor is measuring. I think the technical papers from the sensor developer were posted, and I recall an SAE paper. I remember reading them years back. Capacitance, in combination with the integrated fluid temperature measurement in the sensor, correlates to degradation of the oil. They are measuring oxidation directly, soot in some cases, water in some cases, and additive depletion (the technical phrase used by several different manufacturers of these sensors). I would suggest that the additive depletion is related to TBN, or alkalinity. That would be an indirect measure of additive depletion. As additives are depleted, the TBN drops from the starting point. The computer is calculating the relative drop, and using a map to check if it is in the expected range. If you go to a good oil sampling lab, they will use starting TBN and measured TBN to evaluate oil condition and report on the need to change it, instead of focusing on the trace elements which are commonly referenced, and which refer to engine wear rates instead of oil condition.

You can't measure contaminants without things like mass spectrometers. One sensor manufacturer refers to contaminants, but I think they mean glycol or water. Maybe soot. Particle counters are available, but not rugged enough for mobile applications IMO. And I don't know of anyone using a similar sensor for viscosity measurements.

Edit: my research was a few years back. The link provided in the post above is BMW info but relates to the Continental sensor. I did have the Continental tech paper at some point, and it discussed additive depletion. I went to find the Continental sensor paper as a link, and found this following summary. It seems there are viscosity sensors now. And additive depletion is mentioned as a correlated output from a system using a di-electric capacitance sensor, which is the technology Continental supplies to BMW. Another sensor is listed as monitoring additive condition by relating dispersed soot to undispersed soot, a function of the soot dispersion additives and how many of them are left. Ard, you owe me a beer some day.

Determining Proper Oil and Filter Change Intervals: Can Onboard Automotive Sensors Help?


Jeff

[ard]

We are in general agreement...

My point is that there is a bunch of hand waving going on with many of these lay press pieces, as well as 'trust us, we are omnipotent' from the mfg... and my specific point with quoting JCL was that none of the sensors measre "depletion of the additive package".

Note that I am not saying the capacitance they measure and the ways in which they filter and reduce these measurements are useless, nor am I saying they do not correlate with oil life. They most likely do. We just do know know the correlations or errors or foibles.

We have water, soot and fuel contamination...as well as changes in viscosity...and changing wear metals... does the sensor measure one of these? some of these? or is it simply a correlation wherein multiple aspects combine in non-linear ways, but by testing a correlation has been developed to allow that to say "this oil is probably bad"?

From continental:

The QLT sensor was launched in 1996 to monitor engine oil quality, level and temperature. Two sensors simultaneously and continuously monitor diesel engine oils containing soot. The instrument also monitors nitric oxide and oxidation products in spark-ignited engines, as well as water and fuel contamination. Because these factors influence the oil’s electrical properties and permittivity (ability of a material to resist the formation of an electric field within it), an effective oil condition sensor is achieved, according to the manufacturer. The QLT also has an integrated precision probe that allows it to measure critical temperatures and exact oil levels. It can track temperatures ranging from -40°C to 160°C. The oil level, up to 100 milliliters, is calculated by a second capacitor.

I suppose that somewhere, behind a large NDA, you can find UOAs with correlated long term sensor readings- curves, frequency spectra, etc, etc...


But we dont have it here.


We meet up, Im buying beers for both of you.

[ard]

While we are at it- same article, different sensor:

Voelker Sensors Inc. Oil Insyte
The Oil Insyte sensor uses a patented technology based on the electrical properties of an oil-insoluble polymeric bead matrix (see Automotive Sensor Technologies Explained below for more details). The Oil Insyte employs an in-line method for continuous oil condition monitoring with an LCD readout providing detailed information about oxidation, additive depletion, soot contamination and oil temperature. The technology does not require external calibration standards and reports oil condition independent of viscosity.

According to the manufacturer, the sensor measures key indicators of oil degradation and allows the conventional analyses approach of oil monitoring (sampling and analysis) to be combined into a single more efficient analysis. No assumptions are required as to the condition of the engine or the initial baseline quality of the oil.
The Oil Insyte technology measures oxidation and additive depletion, and has the ability to examine the interdependence between the two. They claim difficulties encountered with sensors that measure only the electrical properties of oil (conductive additives masking the true condition of the oil) are overcome by using a differential technique where the conductivity of the bead matrix is measured relative to the conductivity of the oil. The true polar condition of the oil can then be determined.
The soot detection feature of the sensor determines the amount of undispersed agglomerated soot (vs. dispersed finely divided soot) present in the oil. Depending on the oil’s additive package, the same amount of undispersed soot can be present at 1 percent to 2 percent (for the base oil without dispersants) as a fully formulated motor oil with more than 7 percent soot.

Sounds a bit different than the BMW.continental sensor.

Say, I wonder if there IS some method to BMWs madness that ONLY BMW oil be used...so the sensor has a known baseline?

[JCL]

Originally Posted by ard

Say, I wonder if there IS some method to BMWs madness that ONLY BMW oil be used...so the sensor has a known baseline?

Oil properties may affect accuracy of the algorithms, but he designer would have to accommodate different types of oils. It does highlight the importance of resetting the service indicator when the oil is changed so the system knows to take a starting point sample for the baseline.

Back to the original topic, this is also why it would be important to reset the adaptations when changing the transfer case fluid, even if the flag hasn't been tripped for oil degradation. While the sensing technology is different, it seems reasonable to me to let the system function as designed.

[bawareca]

Originally Posted by JCL

Oil properties may affect accuracy of the algorithms, but he designer would have to accommodate different types of oils. It does highlight the importance of resetting the service indicator when the oil is changed so the system knows to take a starting point sample for the baseline.

Back to the original topic, this is also why it would be important to reset the adaptations when changing the transfer case fluid, even if the flag hasn't been tripped for oil degradation. While the sensing technology is different, it seems reasonable to me to let the system function as designed.

Correct!When i had the "Transfer case oil replacement due" message on my 530xit I tried to erase it,but it was coming back after a few miles drive.Pretty sure the control module goes into some kind of safe or low-torque mode and it will not start the adaptation process unless reset.

[neilrmp]

Originally Posted by JCL

Back to the original topic, this is also why it would be important to reset the adaptations when changing the transfer case fluid, even if the flag hasn't been tripped for oil degradation. While the sensing technology is different, it seems reasonable to me to let the system function as designed.

you are corret JCL, you must reset the adaptation after an oil change.

[toicy4ya]

What is an adaption reset and how do I do it?