International Science Community Association Research Journal of Engineering Sciences 15 2 2026 05 26 Investigation of Hydraulic Oil Quality and Its Influence on Fuel Consumption and Environmental Performance of Motor Graders Operating under Hot and Dusty Climatic Conditions 1 5 EN Alimova Zebo 1 Candidate of Technical Sciences, Professor, Department of Transport Energy Devices, Tashkent State Transport University, Tashkent, Uzbekistan Qurbonov Akrom 2 Tashkent State Transport University, Tashkent, Uzbekistan > Research Paper 2026 2 12 2026 05 26 This study investigates the performance characteristics of UNO HV (HVLP)-46 hydraulic oil used in GR-165 series D motor graders operating under hot and dusty climatic conditions. Physicochemical and spectral analyses were conducted to evaluate viscosity stability, contamination level, wear metal concentration, and additive behavior during service. The results indicate that the used oil contains wear metals such as aluminum (Al), iron (Fe), chromium (Cr), and copper (Cu), as well as atmospheric dust contamination represented by silicon (Si). Degradation products of additives, including sulfur (S), phosphorus (P), and chlorine (Cl), were also detected. The findings demonstrate that maintaining viscosity stability reduces internal leakage within the hydraulic pump, improves volumetric and mechanical efficiency (ηv, ηm), decreases engine load, and consequently lowers fuel consumption and exhaust emissions under severe operating conditions. Copyright@ International Science Community Association