A series of vehicle tests were run in the climate control wind tunnel, at - 18°C (0°F), to characterize the engine warm-up and heat rejection from a 2.3 liter gasoline engine powered Ford Aerostar. The objectives of the tests were to identify and quantify the “waste heat” and to determine how passenger compartment heating could be improved through better waste energy management. It was found that approximately 57 percent of the fuel energy was dissipated as waste heat. More than 30 percent of the fuel energy was lost due to convection and another 20 percent was dissipated in the exhaust gases at the simulated low speed, light load driving conditions. Recovery of a portion of this energy coupled with modifications to the cooling system should lead to greatly improved heater performance.