It has been shown by the authors that car inclination influences the temperatures of different underhood components. Here these effects are analyzed by heat-flux measurements. The results of underhood temperature and heat-flux measurements carried out on a passenger vehicle in wind-tunnel S4 of Saint-Cyr l'Ecole are presented. The underhood compartment of the vehicle is instrumented with 40 surface and air thermocouples and 20 flux meters of normal gradient. Experiments are performed with a specific technique for separate measurement of convective and radiative heat fluxes. Three car position configurations are tested: flat, uphill, and downhill positions. Measurements are made for three different thermal functioning modes. Fluxmetric analysis based on overall heat flux as well as on separate convective and radiative heat fluxes is reported here in order to establish the effects and variation tendencies of car inclination on the temperature-heat flux pair. For most of the tested positions in the underhood top region, the car inclination improves convective heat transfer and penalizes radiative heat transfer. The reduction in radiative heat transfer dominates the convective heat-transfer improvement, resulting in augmentation of the overall heat flux as well as the temperature.