The paper is devoted to optimization of maintenance and repair system of passenger cars. The method is based on the use of profitability as a criterion of optimization. Revenue from car operation is supposed to be uniform during a service life. Costs include price of construction, expanses on utilization (with deduction of income from the writeoff), expanses on repairs of large volume, expanses of other railway services and variable expanses on current maintenance of a car in inter-repair periods that are assumed to change linearly and quadratically during each inter-repair period. The authors propose a method to consider dependence of current repairs cost on a car condition during its life cycle. They also have developed a method of optimization of costs on roundhouse servicing and major overhaul. The proposed methods are realised on C++ language in the form of software package that can be used to control the passenger car repair system and for development of new cars.