Originally Posted by zltm089
hmmm are you sure about this?...
I though that the indicator was just like a "timer"...tells you when approx to change the oil....based on time/ mileage...but it doesn't actually "test" if the oil is still fine or not...
According to BMW CBS bulletin
The type of CBS components supported on a particular model will vary depending on specification and enginetype. Items fall into 2 main groups:
1) Sensor based items
These items are monitored by physical and virtual sensors with some reference being made to variables such as vehicle mileage, driving styles and temperature. Items included in this group are:
-Engine oil – Monitored by the DME/DDE engine control module
-Micro filter/Pollen filter – Monitored by the IHKA climate control module
-Front brake pads – Monitored by the DSC stability control module
-Rear brake pads – Monitored by the DSC stability control module
-Diesel Particulate filter - Monitored by the DME/DDE engine control module
2) Internally calculated items
Certain items monitored by the CBS system do not require physical sensors. These serviceable items still operate under fixed intervals with remaining service life calculated by the instrument cluster based on time and distance. Items included in this group are:
Now looking at TIS, here is the description how oil sensor works;
How it works
The oil condition sensor consists of two cylinder capacitors arranged one above the other. The engine oil quality is measured by the lower, smaller capacitor. Two metal tubes are arranged one inside the other as capacitor electrodes. The engine oil is located between the electrodes as an electrical non-conductor (insulator). The electrical material property of the engine oil changes with increasing wear
and dissipation of the fuel additive. The changed electrical material properties of the engine oil change the capacitance of the capacitor. This capacitance value
is processed in the integrated electronic evaluation unit into a digital signal. The digital sensor signal is passed on as an indication of the engine oil quality to the digital engine electronics (DME). This actual value is processed in the DME to calculate the next engine oil service.
The oil level is determined in the top of the sensor. This part of the sensor is located at the height of the oil level in the oil pan. As the oil level falls, the capacitance of the capacitor falls accordingly. This capacitance value is processed by the electronic evaluation unit into a digital signal and also sent to the DME. A temperature sensor has been fitted to the electronic evaluation unit to measure the engine oil temperature.
The oil level, engine oil temperature and engine oil quality are measured continuously from ignition ON.