In the present work, an experimental investigation has been conducted to analyse the effects of graphene-nanoplatelet (GnP) suspension on the thermal performance of automotive radiator. GnP nanofluids are prepared by dispersing the nanoparticles in distilled water with a concentration of 0-0.3 vol.%. The thermophysical properties of water-GnP nanofluid have been studied with different volumetric concentrations and temperatures. The present study shows that convective heat transfer performance of the automotive radiator could be enhanced by increasing the nanoparticle suspension, heating power, air flow and Reynolds number. The maximum thermal performance enhancement of 275% is achieved for 0.3 vol.% GnP nanofluid at the highest rated heating power. It is also evident that the suspension of nanoparticle has the most significant effect in enhancing the convective heat transfer of automotive radiator, followed by the effects of heating power, air velocity and Reynolds number.