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).

The key document is the 机动车登记证书 (Vehicle Registration Certificate), the green booklet proving ownership. Along with it, the seller should provide the 行驶证 (driving license for the vehicle) and their ID. Verification steps: 1. Check that the VIN/chassis number on the certificate matches the car exactly, stamped on the dashboard and door frame 2. The certificate's 所有人 (owner) field must match the seller's company name or the export agent they claim to work with 3. Look at the registration history pages—frequent transfers in a short period can indicate problem cars being flipped 4. Confirm the car is not marked 抵押 (mortgaged/pledged to a bank) Be cautious if the seller only shows photos of these documents and refuses a live video panning across the original booklet with the day's newspaper. Also verify the export company has 二手车出口资质 (used-car export qualification)—a legitimate exporter will share their license number, which you can cross-check on Chinese commerce bureau websites.

We maintain an absolute skeptical attitude. In addition to regular visual inspections, we focus on checking for sediment accumulation around the sunroof drainage channels and look for water stains under the A-pillar trim and front floor mats. This is the only effective physical evidence to determine if the sunroof drainage holes are blocked, leading to hidden leaks.