Better engine cooling capability remains a desperate challenge in automotive heat management, as traditional water–ethylene glycol coolants regularly manifest limited heat transfer potential. This work investigates the improvement of radiator operation using alumina and titania-based nanofluids as a progressive heat-transfer approach. Nanofluids were produced by ultrasonic dispersion of nanoparticles (0.02–0.08 vol%) in water–ethylene glycol mixtures, followed by experimental testing in a customized automobile radiator test rig at an inlet temperature of 65°C and flow rates of 7–14 L min⁻¹. The specific-heat equation was employed to determine the rate of heat transfer, and differential surface-fluid temperature analyses were used to obtain convective heat-transfer coefficients. The results show that adding alumina and titania nanoparticles notably enhances heat transfer. The hybrid nanofluid (0.06 vol% alumina + 0.02 vol% titania) achieved a highest heat transfer coefficient of nearly 6400 W m⁻² K⁻¹, depicting a 155.6% increase over distilled water and about 60% advancement compared to the base water–ethylene glycol mixture. Radiator efficacy improved by 25–47%, while specific heat capacity was reduced by up to 73%, specifying a faster heating–cooling reaction. The results proposed that nanoparticle-induced micro-convection and improved thermal conduction govern the observed enhancements. The novelty of this work lies in experimentally quantifying the integrated thermal impact of alumina–titania nanofluids under practical automotive conditions, extending existing literature focused primarily on single nanoparticles. These results provide design insights for developing high-efficiency cooling systems in electronic thermal management, automobiles, and renewable-energy heat exchangers.