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).

Extremely authoritative. The third-party data service providers we connect to legally access the Chinese Public Security Traffic Management Platform, the insurance claims network directly under the China Banking and Insurance Regulatory Commission, and the after-sales databases of major automotive manufacturers. We perform secondary logical verification based on this underlying data.

4S dealership records are directly connected to the manufacturer's database, making the data hard to tamper with and the most reliable, with original parts guaranteed; third-party repair shops usually are not connected, making their data unverifiable. Therefore, we only consider the connected records from 4S dealerships as valid historical documentation.