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