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).

Odors are difficult to convey through images, so our quality inspectors conduct subjective smell assessments and record them. For vehicles with severe smoke or mold odors, if deep ozone sterilization is ineffective, we will downgrade the vehicle and mark the report with a red "Odor Warning" at the top.

We can only infer from the existing connected maintenance records. If the records show continuity and adhere to the recommended maintenance schedule, we will assign a high credit score; if there are gaps of tens of thousands of kilometers, we will assume it was not well maintained during that period and alert you.