The present paper focuses on the thermohydraulic performance of a car radiator using Al2O3, CuO, and TiO2 nanoparticles disseminated in an equal fraction in the range of 0.06–0.12% called Ternary hybrid nanofluid (THNF), in water-based fluid, operated at coolant flowrate (CFR) range of 3–8 lpm and fan air velocity of 0.25–1.25 m/s). Moreover, a detailed accentuation has been given on the extensive nanofluid characterization mainly thermophysical properties and its stability, to justify nanofluid durability for the long run (scanning electron microscope, Zeta potential). Performance evaluation criteria (PEC) and friction factors were analyzed to evaluate the penalty in pressure drop for the heat transfer enhancement achieved. The experimental analysis revealed a maximum heat transfer enhancement in the coolant of 14.2% at CFR of 6lpm using 0.12% vol. fraction of THNF. The PEC value found within the limit of 1.0045–1.098 indicates a remarkable heat transfer enhancement on nanoparticle addition. Concurrently fuel elevated temperature improved thermal efficiency by 13.6% at 0.25 m/s of frontal air velocity during a maximum fuel-saving of 14.28% at 50% load on the engine. Hence, the preheating of fuel through the radiator waste heat improves the thermal efficiency, lowers the brake-specific fuel consumption, and saves fuel consumption successfully.