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).

Once the car system (especially in a closed ecosystem) undergoes a major version upgrade, its bootloader is usually locked, preventing downgrades. If this happens, there is basically no solution in an overseas environment. Therefore, we strongly warn: do not blindly insert a USB drive to upgrade while offline.

Unless the previous owner retained the original parts and provided them to us, we usually keep the existing modifications and clearly state in the report "includes non-original modifications." Since the standards for illegal modifications vary by country, buyers should assess whether these modifications can legally pass inspection in their destination country.