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).

Be sure to purchase cargo insurance (all-risk or water damage insurance). In case of damage, claim with the bill of lading, insurance policy, and proof of damage at the destination port.

Because it's not a one-time transaction. Only by ensuring compliance checks, improving after-sales service, and providing parts can a good reputation be established, leading to repeat purchases and long-term cooperation.