With the nationwide full implementation of China VI emission standards and the accelerated phase-out schedule for older vehicles, municipal sanitation departments across the country face multiple challenges in procuring special-purpose vehicles—from regulatory compliance to operational efficiency. Recently, a municipal sanitation department in Chengdu completed the procurement and delivery of a batch of blue license plate sewage treatment trucks. Among them, the Dongfeng D6 chassis solution provided by Chengli Special Purpose Vehicle Co., Ltd. received positive feedback from customers due to its superior rust resistance in hot and humid environments, durability of sealing components, and high-load operational performance. This article uses this case as a starting point to deeply analyze the policy background, vehicle selection rationale, and subsidy stacking strategies—offering practical reference for similar procurement projects. I. Policy Background: China VI Implementation and Phased-Out Vehicle Timeline Since 2021, China VI emission standards have been fully implemented nationwide; all newly purchased special-purpose vehicles must comply with the China VIb requirements. According to the 'Announcement on Implementing the National Sixth-Stage Motor Vehicle Emission Standards' and related local supporting policies, diesel trucks meeting China III or lower emission standards have been restricted from operation—or mandatorily scrapped—in most cities, while China IV vehicles are progressively entering their phase-out window. As the provincial capital and a key city in Southwest China, Chengdu issued relevant policies as early as 2022, requiring the completion of scrapping and replacement of China III (and below) emission-standard commercial diesel trucks by the end of 2025. For municipal sanitation departments, this means that aging sewage treatment trucks, vacuum suction trucks, and other special-purpose vehicles must be replaced urgently. In this case, for example, the legacy sewage treatment trucks typically used China IV or China V chassis—non-compliant with current emissions regulations and increasingly costly to maintain—no longer meet the demands of refined urban sanitation management. Newly procured vehicles must conform to China VI standards to ensure normal registration, annual inspection, and road access rights. II. Case Details: Procurement of Blue License Plate Dongfeng D6 Sewage Treatment Trucks by a Municipal Sanitation Department in Chengdu In early 2026, a municipal unit under the Urban Management Bureau of a district in Chengdu launched a procurement project for a batch of blue license plate sewage treatment trucks. This unit is responsible for sewer cleaning and wastewater treatment operations across multiple old residential communities and agricultural markets within its jurisdiction. Its operating environment is characterized by high temperature and humidity, elevated salinity (due to residual de-icing agents on roads and high groundwater levels), and high operational frequency—averaging over eight hours per day. Following open tendering and comprehensive evaluation among multiple suppliers, Chengli Special Purpose Vehicle Co., Ltd. delivered five units of blue license plate Dongfeng D6 sewage treatment trucks (model reference: CLW5070GSSD6, based on the same Dongfeng D6 chassis platform). According to feedback from the procuring entity, the main considerations for selecting Chengli’s solution included: • Chassis Reliability: The Dongfeng D6 chassis enjoys a large installed base in Southwest China, ensuring abundant spare parts availability and convenient after-sales service and maintenance. • Enhanced Anti-Corrosion Coating: To address Chengdu’s hot and humid climate, Chengli applied reinforced anti-rust treatments to the upper-body tank and critical connection points—including epoxy primer plus polyurethane topcoat—and added localized galvanization to the chassis. • Sealing Component Durability: Sewage