Thermal management describes measures that result in the improved engine or vehicle operation in terms of energetics and thermo mechanics. In this context the involvement of the entire power train becomes more important as the interaction between engine, transmission and temperature sensitive battery package (of hybrid vehicles or electric vehicles with range extender) or the utilization of exhaust gas thermal energy play a major role for future power train concepts.The aim of thermal management strategies is to reduce fuel consumption while simultaneously increasing the comfort under consideration of all temperature limits. In this case it is essential to actively control the heat flow, in order to attain the optimal temperature distribution in the power train components.Particularly against the background of modern, extremely efficient combustion engines, the precise calibration of a fast and consumption optimized heating-up phase on the one hand, as well as the allocation of a sufficient heating output on the other hand, becomes an ever more significant task.To exploit these potentials the development engineer uses modern simulation tools, which help to efficiently quantify different interventions in the thermal system of a power train.Within this article FEV Motorentechnik presents a one-dimensional thermal management model developed on basis of the commercial simulation program GT-Suite. This simulation program describes all relevant thermal inertias, the coolant circuit, the lubrication system, the thermodynamics of the engine and the friction losses depending on local existing boundary conditions as well as a transient vehicle model for different driving cycles and ambient conditions. By adding specific components to the basic models (e.g. map-controlled thermostat, electrical water pump, split cooling, switchable piston cooling jets, exhaust gas heat exchanger etc.) most different measures and control strategies for thermal management are examined and evaluated in detail regarding their effectiveness on fuel consumption. Furthermore the extremely complex cooling systems of electro and hybrid vehicles consisting of low temperature cooling circuit, high temperature cooling circuit and conditioning system for the additional electric components (e.g. traction battery, electric engine, power controller, DC-DC converter) are examined.