Taking into consideration the fact that used oils are considered hazardous and extremely toxic, their subsequent use creates a real threat to the environment. The only effective measure for protecting the natural environment from used oil contamination is collection and controlled utilization. Only appropriate used oil management can guarantee minimal environmental contamination and prevent its irreversible degradation.
The aim of our study was to determine the content of select heavy metal elements in used engine oils originating from agricultural tractors and agricultural machines of varying mileage. The tests were carried out by using the HD XRF method. The researched samples showed a high content of zinc remaining at 726- 1,389 mg·kg^-1. The contents of molybdenum, iron, and copper also were high, at Mo 360-689 mg·kg^-1, Fe 16.5- 267 mg·kg^-1, and Cu 4.63-76.87 mg·kg^-1. Low nickel, manganese, chromium, and lead contents were found in the ranges: Ni 0.14-0.75 mg·kg^-1, Mn 0.41-4.27 mg·kg^-1, Cr 0.36-10.66 mg·kg^-1, and Pb 0.9-13.71 mg·kg^-1. Mercury and cadmium were not found in the tested oils.