Thermal management and energy management offer partly unused possibilities to reduce fuel consumption. A detailed description of the thermal behaviour in order to improve the thermal management of engines requires well adjusted simulation-based optimization models. Within this project, the thermal behaviour of several engines is determined by experimental studies on an engine test bed. The determined data is also used for the verification of the enhanced calculation models. Particular attention was turned to a detailed modelling of the engine friction especially at low temperatures. Furthermore a suitable fuel consumption model, which provides the opportunity to take different electrical loadings into account, was integrated. Modelling of the exhaust system and the gearbox completes the whole model. The developed simulation model offers the possibility to evaluate various thermal management measures and carry out parameter studies, respectively the estimation of maximum potential. Examples for this estimation are warm-up without coolant, reduction of operating materials and the usage of alternative operating materials (PCM-coolant, oil). Further key aspects of this activity are estimations concerning of modified engine components (e.g. oil- and coolant-pump) and the investigations on different cabin heating systems. The ongoing developments in engine technology in the fields of combustion-process and new materials lead to changes within the thermal behaviour of engines thus a further goal is to develop an efficient methodology to adapt the simulation models to new engines rapidly.