I. Scenario Introduction: Sewage Treatment Challenges in Highland Cities Xining is located in the northeastern part of the Qinghai-Tibet Plateau, where the average winter temperature ranges from -8°C to -15°C, dropping as low as -20°C. In late 2024, a municipal sanitation department in the region issued a public tender for a batch of blue-license-plate sewage treatment trucks, specifying requirements including cold-weather engine start-up capability, stable hydraulic system performance, and operability with a Class C driver’s license. After multiple rounds of technical evaluation and solution comparison, six Dongfeng D6 blue-license-plate sewage treatment trucks (model CLW5070GSSD6, chassis-modified by Chengli Special Purpose Vehicles) were ultimately delivered. This article examines the vehicle’s suitability for high-altitude operations based on real-world feedback from drivers. II. Real-World Driver Feedback: Authentic Performance in Low-Temperature Environments Zhang Master, responsible for daily operation and maintenance of these vehicles, brings eight years of specialized vehicle driving experience. He reported that upon delivery in December—when Xining’s temperature had dropped to -12°C—the vehicle’s diesel-powered heater and antifreeze preheating system completed preheating within three minutes, enabling successful single-start ignition. By contrast, his previous vehicle required over 15 minutes of garage preheating. Regarding the hydraulic system, Chengli upgraded to low-temperature hydraulic oil and used cold-resistant rubber hoses specifically for high-altitude, frigid conditions; even at -15°C, the hydraulic boom extended and retracted smoothly without leakage or jamming. The sewage tank is constructed from 3-mm-thick stainless steel and features a 5-cm-thick insulation layer, preventing freezing during transport. Zhang Master emphasized: “In winter, we used to dread frozen tanks—but now the tank’s bottom is equipped with electric heating tapes. Activating the thermal preservation mode after parking ensures the sewage remains liquid overnight, allowing direct discharge into the treatment plant the next morning.” Based on local procurement norms, the unit price of these vehicles is approximately RMB 350,000, positioning them among the higher-specification options within the blue-license-plate category, per publicly available tender data. III. Operational Convenience and Ease of Use for Class C License Holders The Dongfeng D6 chassis features a wheelbase of 3,308 mm, with overall vehicle length kept under 6 meters and width at 2.2 meters—fully compliant with Class C license driving requirements. Li Master, a newly assigned driver at a district urban management bureau, holds only a Class C1 license and had never operated a special-purpose vehicle before. After just half a day of training, he was able to independently complete round-trip operations between residential communities and the treatment plant. Li Master commented: “The steering is light, visibility is better than in passenger cars, and standard-fit rearview camera and radar systems make maneuvering—even U-turns in narrow alleys—effortless.” The vehicle’s electronic-hydraulic control system allows one-touch switching among suction, discharge, and cleaning modes via an in-cab touchscreen, significantly reducing the risk of operational errors. IV. Hydraulic System Stability in Low Temperatures and Winter Maintenance Recommendations To address Xining’s harsh winter conditions, Chengli’s technical team provided a dedicated winter maintenance program: • Hydraulic System: Use L-HV46 low-temperature hydraulic oil (pour point below -30°C); replace hydraulic oil filters every 500 operating hours. • Engine: Use -35# diesel fuel combined with an intake preheating grille to ensure smooth cold starts; add anti-gelling agent every 2,000 km. • Tank Insulation: Factory-standard 5-cm polyurethane insulation layer plus integrated electric heating tape; activate thermal prese