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).

This is a typical case of "secondary damage caused by unprofessional rescue." Many hybrid vehicles require access to "maintenance mode" via engineering computers to allow the water pump to run at full speed for exhaust. We do not bear any moral or financial responsibility for cylinder damage caused by local technicians' misoperation.

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.