I. Case Background: Foton Fengjing Service Vehicle Procurement by a Municipal Sanitation Department in Chengdu. By the end of 2025, a municipal sanitation department in Chengdu initiated a public tender for a batch of Foton Fengjing service vehicles, driven by aging existing fleet assets and mounting pressure from the nationwide full implementation of China VI emission standards. These vehicles are primarily intended for daily inspections, equipment maintenance, and emergency response within their jurisdiction—requiring high operational frequency, low failure rates, and reliable performance under Chengdu’s humid, subtropical climate. According to publicly available tender information, the project budget was capped at approximately RMB 3.171 million, with 12 units planned for procurement at an estimated unit price of around RMB 230,000. During the tender process, Chengli Special Purpose Vehicle Co., Ltd. (hereinafter referred to as "Chengli") secured the contract by offering a comprehensive China VI-compliant chassis solution and extensive customization experience, ultimately delivering 12 service vehicles. Customer feedback confirmed stable performance during high-load monsoon-season operations; the anti-corrosion coating and sealing components successfully withstood Chengdu’s rainy, high-humidity environment. This case serves as the entry point for an in-depth analysis of vehicle selection strategies and subsidy stacking methods amid the China VI transition. II. Policy Context of the China VI Transition and Timeline for Phasing Out Older Vehicles. Effective July 1, 2023, the China VIb emission standard became fully mandatory nationwide for all newly manufactured light-duty vehicles. For sanitation authorities, the phase-out schedule for older vehicles (China IV and earlier) has been clearly defined: China IV diesel vehicles: Banned from operating in urban core zones in many regions; full withdrawal from service expected by 2026. China V diesel vehicles: Subject to driving restrictions in several provinces—including Sichuan—and projected for gradual retirement between 2027 and 2028. New-energy transition: Cities such as Chengdu actively promote new-energy service vehicles; however, conventional fuel-powered service vehicles (e.g., Foton Fengjing) remain indispensable for inspection and emergency response duties—provided they comply with China VI requirements. The current procurement by this Chengdu municipal sanitation department aims specifically to replace its China IV fleet, which has been in operation for over eight years, ensuring regulatory compliance beyond 2026. Chengli’s Foton Fengjing service vehicle solution—built on the Foton Tuoyano chassis and equipped with a China VIb-compliant diesel engine—enables seamless local registration and annual inspection, while also qualifying for regional scrappage-and-replacement subsidies. III. Chengli’s China VI Solution: Environment-Specific Customization for Humid, Hot Climates. Located in the Sichuan Basin, Chengdu experiences average relative humidity exceeding 80% annually, with frequent rainfall from June through September—posing stringent demands on vehicle corrosion resistance and sealing durability. For this project, Chengli prioritized optimization in three key areas: Corrosion-Resistant Coating: Full-vehicle underbody and critical body sections feature electrophoretic primer plus polyurethane topcoat, with minimum dry-film thickness ≥120 μm and salt-spray resistance exceeding 1,000 hours (referencing anti-corrosion specifications of CLW5070GSSD6 water-sprinkling trucks). Sealing Component Durability: Door, window, and equipment-compartment seals utilize ethylene propylene diene monomer (EPDM) rubber—exhibiting superior aging and ozone resistance, extending service life by 30% under 80% humidity conditions. High-Load Performance: To accommodate elevated monsoon-season usage intensity (average daily mileage of 150–200 km), the configuration includes reinforced suspension