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).

If the car has been maintained at an authorized dealer, we can extract the desensitized official maintenance history (including entry time, mileage, and maintenance items) through a paid third-party data provider and provide it to you. If some year records are missing, we will honestly inform you that the "records are incomplete."

Experience turbo lag and power surge during road tests; check for significant oil accumulation at the turbo intake and intercooler connections (slight oil vapor is normal); and use OBD to read the real-time boost pressure peak to see if it meets factory settings.