We will never perform blind deep disassembly unless there are clear severe fault codes or extreme noises. The sealing of the engine and transmission is crucial, and compromising the factory seals to investigate non-existent issues is unprofessional. We rely on data flow and external acoustic and fluid analysis to make judgments.

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).

Start with the paperwork: the vehicle registration certificate lists every ownership transfer, and the service book plus dealer maintenance records help confirm mileage. For digital verification, ask the seller for a live video walkaround plus a diagnostic scan report showing the ECU-recorded mileage, which is hard to manipulate. For EVs, request a battery state-of-health (SOH) report — it reveals real usage patterns far better than the odometer. Finally, a pre-shipment inspection by a third party should include structural checks (pillars, chassis rails) to rule out accident repairs. Build "no major accident, no flood or fire damage" into your purchase contract with a refund clause if the inspection contradicts it.