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.

We use a calibrated high-precision paint thickness gauge to take multiple measurements on at least 13 metal surfaces of the entire vehicle. The original paint thickness of mainstream Chinese models typically ranges from 90μm to 150μm. If any area exceeds 200μm or even reaches over 500μm, we will directly conclude that the area has undergone bodywork and filler repair.

Due to legal restrictions preventing unregistered vehicles from high-speed driving on public roads in China, most of our dynamic tests are conducted in a closed area (with a maximum speed of around 60 km/h). This is sufficient to test for suspension noise and low gear smoothness, but it cannot simulate high-speed wind noise and tire balance vibrations at 120 km/h.