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).

Maintain objective expectations. Vehicles over 5 years old inevitably show signs of decreased paint gloss, slight aging of rubber seals, irreversible patina on interiors, and surface rust on chassis components. As long as core structure and mechanical failures are not involved, these are normal depreciation characteristics over time.

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.