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The engine oil contamination by both particulate matter (PM) and fuel is becoming an important problem since strategies to control pollutant emissions in internal combustion engines (ICE) significantly increase their presence in engine oil. As a consequence, the engine oil loses its tribological properties compromising engine lubrication and leading to potential problems in engine such as wear, corrosion, etc. For that reason, the study of the oil degradation and contamination due to these strategies have a special interest to the engine manufacturers and engine oil formulators. In this paper, the engine oil soot content and fuel dilution is analysed under real engine conditions. The study is addressed from two different but complementary points of views. First, on-line measurements at several engine operating conditions are performed in order to further understand how the soot generation correlates with the oil soot content and other derived problems on oil performance. Then, experimental data available after the experimental campaign is used to calibrate a numerical model, based on Computational Fluid Dynamics (CFD), that estimate the amount of soot particles settled in the engine oil. Results show that soot particles are more present in oil when operating high load-speed conditions and during the Diesel Particulate Filter (DPF) regeneration cycles. Regarding the fuel dilution, delayed post-injections are critical since they significantly increase the amount of fuel in the engine oil. Numerical results also show the relationships between the soot particles generated during combustion and the amount of soot in engine oil, giving an enhanced comprehension of soot-in-oil deposition mechanisms.

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Internal combustion engines (ICE), as a consequence of new pollutant emissions standards, need several emission control strategies (and related procedures) such as Exhaust Gases Recirculation (EGR), Diesel/Gasoline Particulate Filter (DPF/GPF), Selective Catalyst Reduction (SCR) that allow them to comply with complete requirements defined on those standards. These strategies provoke faster degradation of the engine oil and one of the most relevant consequences is an increase in soot contamination level. All of these strategies facilitate the soot generation.Consequently, soot is one of the most important contaminants present in the engine oil and its relevance is still increasing. The main and classic technique to measure the content of soot in oil is Thermogravimetric analysis (TGA), but this technique has certain limitations. TGA needs a long specific procedure and has limitations to measure small concentration of soot in oil. Therefore, the design of an alternative technique to quantifying the soot in oil concentration is acquiring relevance. One alternative can be the Fourier-transform infra-red (FTIR) spectroscopy, but it also has limitations related to small concentrations of soot in oil. This work presents an alternative technique based on the Ultraviolet-Visible (UV-Vis) spectroscopy, which will let us to quantify 2 small soot contents in used engine oil samples and avoiding potential interferences from other typical contaminants or related with the own measurement process such as sample cuvette material.