This study undertook a comprehensive analysis of the eco-efficiency and economic viability of various city buses, focusing on their environmental impact and life cycle costs. Using Life Cycle Assessment (LCA), the environmental footprints of buses, considering their type and recycling country, were assessed. Results highlighted the generally lower environmental impacts of Compressed Natural Gas (CNG) buses compared to diesel and electric buses. Furthermore, Life Cycle Cost (LCC) evaluations showed diesel buses as the least economical, with Chinese CNG buses emerging as the most cost-effective over their lifespan. Additional analysis using the PCA-DEA model indicated the superior efficiency of certain bus units, especially both the Chinese CNG recycled in China and India. Sensitivity analysis further revealed that environmental categories with higher sensitivity ratios can achieve complete efficiency with modest improvements. Overall, the findings suggest that CNG buses, particularly those from China, present an eco-friendly and economically sustainable choice for urban transportation.