This study presents the development of an interactive automotive simulator aimed at optimizing supply chain performance by digitally integrating production planning, inventory management, and supplier cost analysis. The tool provides real-time visualization and adjustment of variables such as on-hand inventory, daily consumption, and lead time, generating dynamic Days of Inventory on Hand (DOH) calculations and alerts for Pull-In and Push-Out scenarios. Through simulated production and procurement strategies, users can evaluate the effects of operational decisions on inventory stability and cost efficiency. The simulator incorporates supplier evaluation using average cost, lowest price, and avoided cost metrics to support informed sourcing and negotiation. Developed as a single page. React application with interactive dashboards, it enables agile decision-making and continuous improvement aligned with Lean and Six Sigma principles. Results show strong potential for cost reduction, better stock control, and improved responsiveness in automotive manufacturing, while providing a foundation for future AI, digital twin, and sustainability-based enhancements.