4S dealership records are directly connected to the manufacturer's database, making the data hard to tamper with and the most reliable, with original parts guaranteed; third-party repair shops usually are not connected, making their data unverifiable. Therefore, we only consider the connected records from 4S dealerships as valid historical documentation.

The technician will start the vehicle and turn on the air conditioning system, measuring the actual temperature at the vents at the lowest and highest settings with a thermometer; at the same time, they will connect a manifold pressure gauge to check if the refrigerant pressure in the high and low pressure lines is within the normal range, determining if there is a chronic refrigerant leak.

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.