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.

This involves personal privacy, and we have no right or ability to retrieve personal driving violation records from the traffic police system. We can only infer if there was aggressive driving by checking if the engine has been reprogrammed with a higher-level ECU (stage 1/2) or if the transmission has a history of severe overheating.

Many car owners do not have their first maintenance done at authorized dealerships, leading to gaps in early data. In such cases, we do not blindly trust the odometer; instead, we analyze the tire production dates and wear levels, as well as the depth of grooves on the brake disc edges, using the "gold standard" of physical wear to infer the intensity of early use.