Beyond the 'three-documents-consistent' rule, commodity classification (HS codes) and inspection-supervision interpretation form the second watershed for the landed cost of re-exported oil products. Threshold specifications for base oil, paraffin wax and petroleum coke — viscosity index, drop/melting point, sulphur and ash content — directly determine the applicable tariff line and the required certificate package. SNSUC Research Institute recommends replacing 'settle it on arrival' with 'classification upfront', backed by on-chain attestation of inspection reports and certificates of origin.