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Cooling drag is the increase in the total drag due to the internal flow in the cooling system. Because of the high flow resistance in the heat exchanger the momentum of the fluid needed for engine cooling usually is dissipated nearly completely. The resulting drag penalty can be approximated by the so called ram drag. For ground vehicles the cooling drag is typically lower than this approximation due to positive interference of the cooling flow with the general flow around the vehicle. Different mechanisms for the positive interference have been described in the literature. Inlet interference as well as outlet interference can result in significant reduction of the share of the cooling drag. Positive outlet interference is obtained, when the remaining kinetic energy of the cooling flow contributes significant thrust to the overall momentum balance.

For the aerodynamic development of an aircraft the induced drag is an important quantity and it has a significant impact on the design of the wing. The induced drag corresponds to the power requirement of the wing to generate the necessary lift. In many cases this is the dominant source of drag for aircraft. In ground vehicle aerodynamics the concept of induced drag up to now has attracted much less attention. This is partly due to the fact, that vehicle aerodynamicists usually optimize the vehicles to generate little or no lift. The second reason is that it is much more difficult for a ground vehicle to separate the total drag into the different contributions. During wind tunnel tests of vehicles with and without ground simulation some astonishing results were found, especially when comparing results for different rear end shapes.