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).

To prevent intermittent failures due to aging of the resistance wire, we will start the engine and set the seat heating/ventilation to maximum for at least 5 minutes, confirming significant temperature changes or airflow output in the cushion and backrest using an infrared thermometer or body sensor.

Supply and demand determine prices. In the Chinese market, mainstream colors like black and white have much higher resale values and market circulation speeds compared to less popular colors (like pink or bright green). Therefore, there is a price difference of thousands of RMB for specific colors at the procurement level.