The environmental impact of heavy-duty vehicles (HDVs) poses significant challenges in reducing emissions. This study introduces a Life Cycle Optimization (LCO) framework for HDVs, integrating mathematical optimization algorithms into product development to achieve eco-efficient and eco-effective designs. Building on life cycle engineering (LCE), the framework incorporates a five-step process linking product design, life cycle inventory, impact assessment, and optimization. Pre-tested on a theoretical 40t long-haul HDV, it demonstrates its ability to guide eco-effective design while maintaining functionality. Its modular structure adapts to various system levels.