The most recent developments in nanotechnology have lead to improvements in original uses of nanofluids in car motor cooling. In the present study, enhancement of car engine radiator by TiO2-water nanofluid as a coolant of car engine radiator was investigated experimentally. In order to determine the effect of TiO2-water nanofluid on radiator's performance, experiments were performed with pure water and TiO2-water nanofluid separately and results were compared with other studies on vehicle engine system FIAT DOBLO 1.3 MJTD ENG. The main objective was to check the aspects of heat transfer of the TiO2-water nanofluid as a substitution to the customary coolant system. For this purpose, experiments were carried out using a TiO2 nanofluid with 0.1, 0.2 and 0.3% volume concentrations with flow rates of 0.097 and 0.68 m(3)/h in laminar floe region, where Reynolds number ranged from 560 to 1650. Our results show that the friction factor decreases when Reynolds number and the volume concentration are increased. Moreover, TiO2-water nanofluid with 0.2% concentration can enhance the effectiveness of car radiator by 47% as compared to 0.1 and 0.3% concentrations and pure water as a coolant. Finally, the average heat transfer coefficient was directly affected by the increase in Reynolds number and volume concentration fraction of the nanofluid. (C) 2018 Karabuk University. Publishing services by Elsevier B.V.