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.