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.

Our bulk discounts are not simply calculated by the number of units, but by shipping batches. Typically, consolidating enough for a 40-foot container (which can hold 2-3 vehicles, depending on size) can waive some logistics fees; purchasing more than 5 units at once triggers tiered discounts.

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).