In this book the longitudinal behavior of road vehicles is analyzed. The main emphasis is on the analysis and minimization of the fuel and energy consumption. Most approaches to this problem enhance the complexity of the vehicle system by adding components such as electrical motors or storage devices. Such a complex system can only be designed by means of mathematical models. This text gives an introduction to the modeling and optimization problems typically encountered when designing new propulsion systems for passenger cars. It is intended for persons interested in the analysis and optimization of classical and novel vehicle propulsion systems. Its focus lies on the control-oriented mathematical description of the physical processes and on the model-based optimization of the system structure and of the supervisory control algorithms. This text has evolved from a lecture series at ETH Zurich. Prerequisites are general engineering topics and a first course in optimal control theory.