The processes of degradation of engine oils operated in passenger cars of a uniform fleet of 25 vehicles were analyzed for oxidation content using infrared (IR) spectroscopy. As part of the experiment, the changes in engine oils occurring during actual operation (under conditions which can be described as “harsh”, i.e., short distance driving, frequent starting of the engine, and extended engine idling) have been observed. An evaluation of the Fourier transform infrared spectroscopy (FTIR) spectrum of an engine oil sample was presented. The infrared spectra of both fresh and used oils were recorded with the Thermo Nicolett IS5. The tests were conducted according to the Appendix A2 of ASTM 2412. For the used engine oil differentiation process, FTIR spectra were analyzed in the regions of 1,700–2,000 cm⁻¹ and 3,600-3,700 cm⁻¹. The FTIR spectrometry is demonstrated to be effective for the analysis and monitoring of processes of oxidation and shown to provide rapid and accurate information relating to the aging process of engine oils. The results may facilitate decision-making regarding the service life of engine oils. The achieved dependencies can make it possible to upgrade the sensor assembly consisting of an FTIR source.

This article focuses on the results of investigations of selected heavy metals (Mg, Fe, Ni, Cu, Zn, Pb, Ca, Cr and Al) in engine oils of various manufacturers. The measurements were made using atomic absorption spectrometry (AAS) THERMO-iCE 3000 Series. The aim of the study was to determine the concentrations and the direction of changes of those heavy metals and to determine the statistical relationship between the car mileage and the concentration levels of individual trace elements. Statistical analysis of the test results showed significant changes in iron and copper concentrations in engine oil, depending on the engine's operating history.

This article describes the processes of degradation of five engine oils belonging to the same SAE (Society of Automotive Engineers) viscosity class but launched by different manufacturers. The direction and intensity of changes in the total acid number have been analyzed. As part of the experiment, the changes in engine oils occurring during operation have been examined. The operating conditions throughout the test can be described as “severe,” that is, frequent starting of the engine, short distance driving, and extended engine idling. All engine oils were operated in passenger cars of a uniform fleet of 25 vehicles. The total acid number was determined in accordance with the ASTM D664. The obtained results have led to the development of a statistical model enabling to calculate average predictive values of the total acid number for a given mileage. The results may facilitate decision-making regarding the service life of engine oils.