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 use quantitative standards. Minor scratches less than 3 cm that do not reach the base coat (which can be polished) are considered normal wear; scratches over 3 cm deep to the base coat or dents larger than 2 cm in diameter will be highlighted in the inspection report's "Appearance Defect Distribution Map" with close-up photos.

We use a calibrated high-precision paint thickness gauge to take multiple measurements on at least 13 metal surfaces of the entire vehicle. The original paint thickness of mainstream Chinese models typically ranges from 90μm to 150μm. If any area exceeds 200μm or even reaches over 500μm, we will directly conclude that the area has undergone bodywork and filler repair.