Automotive systems fundamentally improve passenger comfort, safety, economy, and security. However, while many design problems related to requirements such as real-time performance and safety and reliability have become manageable, cost-effectiveness and time-to-market remain a challenge for the automotive industry. Product lines are a promising approach in this respect because they permit the strategic reuse of core assets during system development. However, to gain significant economies of scope within a product line approach, systematic planning and continuous management of variability throughout the development process is required. In this article, the authors discuss the value of variability in product lines and describe their approach to modeling and using variability, which evolved from their work with several industrial case studies at Bosch.