The mining industry of the Republic of Armenia makes an important contribution to the country’s economy, developing rapidly and providing up to 33 % of the share of the raw materials sector. In order to enhance performance and productivity of mining companies in the Republic of Armenia, it is necessary to increase operating efficiency of process equipment and, first of all, of heavy-duty dump trucks, in particular, the BELAZ family. It should be noted that the considerable maintenance and repair burden raises specific demands for the reliability and operability of systems, components and aggregates of dump trucks, in particular, internal combustion engines. The studies have found that the downtime of BELAZ dump trucks because of engine malfunctions accounts for 29 % of the total balance of downtime, which directly leads to the increased operating costs and reduced productivity. The power units of dump trucks have no backup, and, as a result, failure of a unit or a few units will lead to failure of the car as a whole. Power units have closed lubrication systems, failures of which account for a significant share in the total balance of failures of motor vehicles—from 38 to 48 %. In this regard, it is advisable to have information about technical condition of the machine from such source as the lubricating oil. Based on such information from the spectral analysis of the worked oil, it is possible to identify the most unreliable element of the system and perform the entire range of maintenance and repair that allows effective control over technical condition of the car. In order to determine the worked oil characteristics, engine oil of 11 BELAZ dump truck, having different operational life lengths, were subjected to the spectral analysis. The research proved high performance characteristics of engine oil G-Profit MSI Plus SAE 15W-40 API Ci-4/SL and confirmed its application advisability in operation of dump trucks in open pit mines in Armenia.