In the quest for higher performance and energy efficiency, nanofluids play a crucial role in revolutionizing heat transfer processes. Their innovative properties offer enhanced thermal management and sustainability across various applications. In this work, novel nanofluids were prepared utilizing environmentally friendly nanoparticles made of Powdered Activated Carbon supported Carbon Nanotubes (PAC-CNT) dispersed in a base fluid made of a binary eutectic solvent consisting of ethylene glycol and imidazole. Compared to traditional working fluids, this base fluid is distinguished by its thermal and chemical stability and low vapor pressure. Six nanofluids were prepared with different nanoparticle concentrations (0.08, 0.1, and 0.12 wt%). These were mechanically dispersed in two systems of base fluids with 1:2 and 1:3 molar ratios of imidazole to ethylene glycol. The stability of the nanofluids was tested by measuring their zeta potential. The rheological behavior of the working fluids was determined at different shear rates. An experimental investigation was conducted to find the effect of temperature, nanoparticles concentration, and base fluid composition molar ratio on the thermophysical properties of the base fluids and the nanofluids. The lower base fluid ratio achieved less viscosity. The viscosity increments with adding NPs were higher in nanofluids with the (1:3 IM:EG) system. There was a slight change in density with the increasing nanoparticles load, and the density of all tested fluids decreased with temperature. Determining the pumping requirement for nanofluids is also essential for heat transfer applications. A model was used to estimate the pumping power demand of the nanofluids by considering their rheological characteristics and their measured density and viscosity. The interactions between the nanoparticles and the base fluid molecules affected the enhancement of the thermal properties of the nanofluids. The nanofluids containing 0.08 wt% of nanoparticles achieved a maximum enhancement in specific heat in both base fluid systems. These enhancements reached 10% and 44%, respectively. The thermal conductivity (TC) was also enhanced by adding nanoparticles to the base fluid. A remarkable 273% increase in TC was achieved with a nanoparticles concentration of 0.08% in the first system (1:2 IM:EG). On the other hand, the improvement in TC was lower in the second system as it reached 57% with 0.08 wt% nanoparticles content. This research contributes valuable insights into the potential applications of the studied nanofluids for enhanced heat transfer performance in various engineering and industrial applications.