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).

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.

We will directly check the registration certificate (the big green book) and count the number of changes.