I. Case Background: Sludge Removal Requirements of a Street Environmental Maintenance Unit in Tianjin Tianjin is located in northern China, where winters are extremely cold, with minimum temperatures reaching -15°C to -20°C. Additionally, the city’s aging drainage network is prone to urban flooding during the rainy season. A street-level environmental maintenance unit (hereinafter referred to as “the Unit”) launched a procurement initiative for sludge removal vehicles in autumn 2025, targeting the following key challenges: Freeze-Resistant Starting Performance: The vehicle must start reliably at -20°C, with no risk of hydraulic fluid solidification. Low-Temperature Hydraulic Stability: Hydraulic oil must retain fluidity during winter operations to prevent hose rupture or sluggish actuator response. Winter Maintenance Plan: Comprehensive daily maintenance guidelines tailored to northern low-temperature conditions to minimize failure rates. The Unit ultimately selected the Dongfeng single-cab blue license plate sludge suction truck with 5-cubic-meter capacity and commissioned Chengli Special Purpose Vehicle Co., Ltd. (hereinafter referred to as “Chengli”) for delivery. According to publicly released tender information, the procurement budget was controlled at approximately RMB 310,000–354,000 per unit, with an average unit price of around RMB 290,000; a total of two units were procured. II. Operational Suitability: Selection of Sludge Suction Trucks for Light-Duty Municipal Applications Sludge suction trucks are primarily used for cleaning and unclogging urban drainage pipes, stormwater inlets, and septic tanks. Operational characteristics specific to Tianjin include: Light-Duty Municipal Use: Narrow streets require compact, blue-license-plate vehicles operable with a Class C driver’s license and overall length not exceeding 6 meters for enhanced maneuverability. 5-Cubic-Meter Capacity: Each operation can handle approximately 5 cubic meters of sludge—ideal for routine maintenance frequency. Dongfeng Chassis: Nationwide warranty coverage, readily available spare parts, and high market penetration in northern China ensure lower maintenance costs. To meet these requirements, Chengli recommended the CLW5070GSSD6 model sludge suction truck (reference announcement model), with the following specifications: Parameter Specification Notes Chassis Model Dongfeng Single-Cab EQ1075SJ3CDF Nationwide warranty Tank Volume 5 cubic meters Blue license plate; operable with Class C license Gross Vehicle Weight (GVW) 7,360 kg Complies with regulatory requirements Engine Model Yuchai YCY24140-60 China VI emission standard Cold-Weather Starting System Glow plugs + intake air preheater Rated for -20°C operation Hydraulic System Low-temperature hydraulic oil (pour point: -30°C) Ensures stable winter performance Delivery Lead Time 7–15 days Standard models shipped from stock Reference Landed Price Approx. RMB 290,000 Tax-inclusive; based on publicly disclosed tender data III. Chengli’s Tailored Solutions: Three Core Guarantees for Winter Operations in Tianjin 1. Freeze-Resistant Starting Performance: One-Touch Start at -20°C Chengli equipped these sludge suction trucks with a standard engine preheating system (glow plugs + intake air preheater), paired with low-temperature engine oil (0W-40 grade). Field tests conducted in Tianjin’s winter confirmed reliable starting after overnight parking (8 hours) even at sub-zero temperatures. Customer feedback stated: “During last December’s cold snap, the vehicle started successfully on the first attempt at -18°C early in the morning—more reliable than competing brands operating in the same area.” 2. Low-Temperature Hydraulic Stability: Hydraulic Oil with -30°C Pour Point The hydraulic system powers critical functions such as tank lifting and suction arm operation. Chengli selected specialized low-temperature hydraulic oil with a pour point as low as -30°C. At -20°C, its viscosity remains stable, effectively preve