in regards to oil analysis....DRUM ROLL........OXIDATION AND NITRATION
Both are direct indicators of the oils break down. Also for systems utilizing oil condition sensors (MB, BMW etc) the engines ECU can monitor directly the oils condition by reading the oxidation characteristic which can be read via a capacitance check of the oil.
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 oil 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.
Oil analysis remains a very good indicator to spot a trend, this is the whole point of an oil analysis to determine wear trends and overall condition of the oil.
When digesting a samples data, you need to take into account a particular engines wear characteristics and specific metal components of the sample that stand out from other engines. For a VW, Copper, Nickel, Iron and Aluminum distinguish a VW engine from other engine types due to the design and makeup of the internal bearing surfaces.
If you suspect a condition where damage is suspect, Ferrorgraphy remains the best option to identify the exact nature of the problem by analyzing the specific nature of the process that removed the metals. Also this remains the only method to analyze the particles greater than 4 microns in size which Spectronalysis cannot detect.