We use two steps: 1. Insert a medical-grade endoscope through the spark plug hole to visually inspect cylinder wall scratches and carbon buildup on the piston top; 2. Extract an engine oil sample to check for large metal debris or emulsification (caused by coolant leakage).

We will never perform blind deep disassembly unless there are clear severe fault codes or extreme noises. The sealing of the engine and transmission is crucial, and compromising the factory seals to investigate non-existent issues is unprofessional. We rely on data flow and external acoustic and fluid analysis to make judgments.

For B2B large customer orders, a "sampling + full inspection" dual regulation is adopted. Core parameters (no major accidents, no water damage or fire) are subject to 100% inspection per vehicle; appearance and condition are uniformly graded (e.g., uniformly purchasing Grade A), and panoramic images of all vehicles in the batch along with a core indicators comparison list are provided before shipment.