This master's thesis looks into the plug-in-hybrid-electrical-vehicle development project (PHEV project) of the company Magna Steyr Battery Systems and its potential for improvement. In the preliminary theoretical considerations the areas of total quality management and the quality management system Six Sigma will be closely examined, as well as the main methods, tools and the forms this takes. The sample phases and milestones prevalent in the automotive industry are discussed. The analysis starts with a reconstruction of the P2-80 and P2-50 projects carried out as part of the PHEV project. To do this, the product development processes and their (completion) dates will be considered and compared with the existing milestone checklists of the individual project areas. This work focuses on carrying out and evaluating interviews with experts (project members) across all departments and hierarchies. 25 experts were interviewed one-on-one using the qualitative survey method and asked about the improvement potential of the PHEV project. The analysis showed 49 inefficiency factors, which in a next step were weighted and ranked with regard to cost, duration, deadline and quality. Then the top 3 inefficiency factors were looked at in more detail. In the "change management" area the numbers of changes in the sample phases are highlighted and any costs incurred that way are represented using the costing model. During the investigation into the change processes the inefficiency factor "internal processes" and the associated IT systems, originally in sixth place, proved to be so unfavorable that it had to be moved to third place. For the inefficiency factor "personnel development", which is in second place, the company's staff turnover over the course of the four-year project was looked into. Further discussions were conducted with individual module group leaders to ascertain the development of staff turnover. This also includes project-based staff turnover, i.e. staff changes in the PHEV project. Finally suggestions for improvement are made to help prevent the top 3 inefficiency factors from arising in future projects.