The article presents the course and characteristics of changes in the physico-mechanical properties of hydraulic oils used in single-bucket excavators operated in rock material mines. The methodology and results of research into the changes in properties of hydraulic oils of HV quality and VG 46 viscosity are presented. Based on the obtained data from monitoring hydraulic oil wear processes, analysis was carried out on the influence of the time and type of work performed by excavators on the rate of oil degradation. During the conducted research, measurements were taken of hydraulic oil parameters, such as the degree of contamination with solid particles, conductivity, dielectric permeability, and operating temperature, etc. The measurement results formed the basis for identifying changes in the physico-mechanical properties of the oils and determining their causes. The conclusions drawn from the research can be used to optimize hydraulic oil replacement processes and service activities for the hydraulic systems of excavators operating in rock material mines. Apart from regular monitoring of the condition of hydraulic oil and analysis of its physico-mechanical properties, this has a decisive impact on the proper functioning of excavator hydraulic systems and on preventing failures and damage to such systems.