<p>This study investigates the thermophysical properties of mono and hybrid nanofluids based on TiO₂ nanoparticles dispersed in bidistilled water (DDW), with the addition of CuO, ZnO, and Al₂O₃ at a total volume concentration of 4 %vol in a 1:1 ratio. Nanofluids were synthesized using a two-step method with ultrasonic dispersion and surfactant stabilization (SDBS, 1:0.1 ratio). Thermal conductivity was measured using the transient hot wire method, while kinematic viscosity was assessed across a temperature range of 293 K to 333 K. Results showed that all nanofluids exhibited improved thermal conductivity and higher viscosity compared to pure DDW. Among them, the TiO₂–CuO/DDW hybrid demonstrated the best overall performance, with a thermal conductivity increase of up to 14 % and the lowest relative increase in viscosity. In contrast, TiO₂–Al₂O₃/DDW showed the highest viscosity increase (up to 140 % at 293 K) and the lowest conductivity enhancement. Additionally, the experimental thermal conductivity data were compared with theoretical models, revealing that the Maxwell model consistently showed the closest agreement, with minimal deviations across all nanofluids (e.g., MAPE: 1.1 % for TiO₂ and 1.2 % for TiO₂–ZnO). In terms of viscosity modeling, the Maïga model provided the most accurate predictions in most cases, particularly for TiO₂–CuO (MAPE: 4.3 %), while the Pak-Cho model significantly overestimated viscosity in hybrid nanofluids, with errors exceeding 100 %. These findings suggest that CuO and ZnO nanoparticles are more effective than Al₂O₃ in improving heat transfer while minimizing flow resistance, making it better suited for practical thermal applications.</p>