For how long must a vessel retain the Oil Record Book on board?

A vessel must retain the Oil Record Book on board for a minimum of three years from the date of the last entry. This requirement is established under MARPOL Annex I, which regulates the discharge of oil and oily mixtures from ships. The Oil Record Book serves as an essential document for monitoring and controlling oil discharges, ensuring compliance with international regulations, and maintaining marine environmental protection.

The three-year retention period allows port state control officers and other authorities to inspect the book during boardings and verifications. Keeping this record for an adequate duration is crucial as it provides a historical account of a vessel's oil management practices, helping to identify patterns or potential violations over time.

The other options do not meet the established legal requirements for record retention and would not be sufficient for compliance with international maritime regulations governing pollution control.