Oil Record Book Part I: 10 Entries Engineers Get Wrong

Updated 29 September 2026 · marpol, oil-record-book, engine-room, port-state-control

The Oil Record Book Part I entries engineers most often get wrong are ordinary ones, not exotic mistakes. A line is missing its item number — the specific checklist line, inside a code, for exactly what happened. Or it carries the wrong code letter, the single letter that marks what kind of operation was logged. A run of the oily water separator (OWS, the machine that cleans oily bilge water before it goes overboard) is logged with no stop position. A bunkering entry — the record made every time fuel or lube oil is pumped aboard — has no total quantity. A correction has been painted over in white-out instead of fixed properly. None of these faults is unusual. Each one gives a Port State Control officer — the inspector who checks a ship's paperwork — a reason to look harder. Reading closer is how a small slip turns into a longer inspection. That longer inspection costs the ship hours it did not plan to lose. In a bad case it costs a missed sailing slot or extra berth fees, both of which show up as real money lost.

Nobody publishes a real frequency ranking of these errors. The guidance checked for this piece came from flag states and inspection guides. A flag state is the country whose flag a ship flies, and it sets rules the ship must follow. All of the guidance describes the same recurring faults. None of it counts how often each fault happens. So the order below follows how an inspector tends to read a page: code, content, timing, signatures, then the numbers.

What Oil Record Book Part I covers

Part I is the machinery space book, kept in the engine room rather than the cargo office. It records bilge discharges, sludge disposal, bunkering and fuel transfers. A Marine Inspection app guide, checked in September 2026, says Part I applies to ships of 400 gross tonnage and above. It also applies to oil tankers of 150 gross tonnage and above. Gross tonnage (GT) is a ship's official size measure, not its weight, and it decides which paperwork rules apply. The record format and this threshold both trace back to MARPOL Annex I. That is the international treaty chapter that sets the rules for preventing oil pollution from ships. The sources checked for this piece did not include the MARPOL Annex I text itself. So treat the 400/150 GT figures as reported by a secondary guide, not as independently confirmed. Check them against your flag state's own notice before an inspection. You can also check them against your class society, the private company that surveys the ship and issues its certificates. Examples include ABS (the American Bureau of Shipping) and DNV, two of the companies that do this work.

This matters because most errors come from treating the book as a diary instead of a structured form. Every line has to fit a code, an item number and a narrative that someone who was not on watch can follow. Get it wrong, and an inspector spends longer on your ship instead of clearing it. Extra hours at the berth can mean a missed sailing window, and in a bad case, a detention that keeps the ship off charter.

The mistakes at a glance

The table below sums up each recurring error, what the inspector sees, and the fix that closes it. Details follow in the next section.

The Oil Record Book Part I entries engineers most often get wrong

Each fault below comes from flag state guidance or inspection guides, and each one has a plain fix that can be applied on the next watch.

Code letter, item number or narrative left out

An entry without its code letter, item number and narrative is incomplete. Every Part I line needs three things. First, a code letter: a single letter from the book's own code table marking what kind of operation happened. Second, an item number: which line of that code's checklist applies. Third, a narrative in plain words. The Bahamas Maritime Authority's notice on MARPOL oil record books (MN056, checked September 2026) says an entry counts only when all three are present. The narrative has to name the exact operation and carry the details that apply: quantity, time, position, and a disposal reference. A disposal reference is the receipt or record showing where the waste oil actually went.

The trap is the half-entry. An engineer writes a code letter and a quantity, planning to finish the line after the watch, and then forgets. On the page it looks like a record. To an inspector, it is a missing one, and a missing entry is the fastest way to turn a routine boarding into hours of extra questions.

The wrong code for the operation

The code must match what physically happened. Every Oil Record Book has its own printed table at the front, and that table — not this article — is what an inspector will hold you to. The Marine Inspection app guide (checked September 2026) gives a common example. A sludge transfer means pumping the oily residue collected in the sludge tank ashore. That gets written under Code D (bilge water discharge) when it should be Code C (collecting and disposing of oil residue, or sludge). Both codes cover oily residue from the engine room, so the two are easy to mix up at the end of a long watch. The cost of mixing them up is not cosmetic. A wrong code is exactly the kind of mismatch that makes an inspector stop and dig further. Digging further means hours added to a port call the ship did not plan for. Every one of those hours is money the ship is not earning. This piece's sources describe the error, but they do not reproduce the full official code table. Check the key printed in your own Oil Record Book before you rely on the letters above.

Bunkering causes the same kind of mix-up. Bunkering just means taking on fuel or lube oil while alongside or from a barge. A 2026 training article from Sailr Network says engineers sometimes log lube oil bunkering under Code G, the code kept for accidental or other exceptional discharges of oil — a different kind of event entirely. In the current MARPOL Part I code table, bunkering of fuel or bulk lubricating oil belongs under Code H instead. Mixing up G and H matters because Code G on the page reads as an accidental spill, and that is not a word you want attached to a routine bunkering job when an inspector is reading it. Check the code table printed at the front of your own book before relying on any article, this one included. The letters have changed with past amendments and could change again; see the section on upcoming changes below.

Entries made late or rebuilt from memory

Entries are due on completion of the operation, or without delay. The Bahamas notice (checked September 2026) says the person directly responsible should make the entry. When a rating — a crew member who is not a licensed officer — carries out the work, the responsible officer is the one who has to write it up.

The Marine Inspection app guide (checked September 2026) recommends completing entries within two hours. It labels that figure as best practice, so treat it as a sensible habit and do not quote it as the legal deadline. Rebuilt pages are easy to spot. They show the same pen, the same pressure and the same neat spacing across operations that happened days apart.

Missing times and positions, especially on OWS runs

Time, quantity and position are the details most often required, depending on the operation, according to the Bahamas notice and a US marine survey guide (both checked September 2026). The Sailr Network training article from 2026 singles out missing stop times and incomplete start and stop positions during oily water separator operations.

This error has a mechanical cause. The start gets written when the pump is switched on and the engineer is still at the separator. The stop happens later, often at a watch change, and nobody goes back to close the line.

Bunkering entries without port, duration or total

A bunkering entry needs the port, the duration and the total quantity. The Sailr Network training article (2026) names all three as fields engineers leave out. It also points to lube oil bunkering as the one most often skipped entirely.

The paperwork behind a bunkering job is checked twice: once for the fuel itself and once for the Oil Record Book entry. Matching the two saves real time. The bunker delivery note (BDN) is the supplier's own record of what was actually pumped aboard. If the Oil Record Book total does not match the BDN, an inspector can hold the ship at the berth to sort out the discrepancy. Every extra hour alongside is an hour the ship is not earning, whether that shows up as a missed slot on its next voyage or a day lost off its next charter. If a bunker checklist is already in use for the fuel-quality side, the simplest fix is to add the Part I entry as its last step, right after the BDN is signed. That way the two numbers get compared while the paperwork is still in hand, rather than days later when nobody remembers the details. Our MARPOL Annex VI fuel oil sampling and bunker delivery note checklist has the full steps for the fuel-quality side of the same bunkering job, covering MARPOL Annex VI — the separate treaty chapter that governs fuel oil quality and air emissions.

Corrections that hide the original

A correction must leave the original readable. The Bahamas notice (checked September 2026) describes a single thin line through the wrong entry, with the amendment dated and signed. It also says necessary amendments should be made within 24 hours of the operation and endorsed by the Chief Engineer or Master and the officer responsible.

The Sailr Network training article (2026) lists white-out, scratched-out entries and illegible text as common mistakes. From an inspector's side, a blot of correction fluid is worse than the error underneath it, because it removes the evidence of what was written first.

Unsigned operations and missing page endorsements

Every completed operation needs the signature of the officer in charge. Each page also needs review by the Chief Engineer or Master, according to the Bahamas notice (checked September 2026). The Marine Inspection app guide (checked September 2026) names unsigned operations and a missing Master endorsement as recurring inspection findings.

Signing is the step people leave for later, because it feels like admin. The fix is to sign at the same moment you write, and to make page review a fixed item on the chief's routine before arrival.

Blank lines and broken chronology

Entries must run in chronological order in the designated spaces. The Bahamas notice and the Liberian registry instructions both say so (checked September 2026). The Sailr Network training article (2026) also warns against leaving blank lines.

The research does not show that every flag or port treats a blank line as a separate deficiency. A gap still invites the question of what was meant to go there, and that is a conversation you do not want during an inspection.

Quantities that do not reconcile

Inspectors compare the book with other records — a process called reconciliation, which just means checking that different logs of the same oil agree with each other. Liberian registry guidance (a 2012 marine advisory, checked September 2026) says officers may check entries against the electronic record kept by oil monitoring equipment. It adds that a mismatch between the two can contribute to detention, meaning the ship is held in port until the problem is fixed. The Marine Inspection app guide (checked September 2026) lists unreconciled sludge or bilge quantities as a common error.

Measurement is imperfect, and the regulator knows it. A 2010 Liberian marine operations note (checked September 2026) says gauge accuracy, temperature changes and clingage all affect recorded quantities. Clingage is the oil that sticks to a tank's walls after it is supposedly empty, and it throws sounding figures off by a small, predictable amount. That explains small differences. It does not excuse a number you know to be wrong.

A missed entry recorded in the wrong place

If an entry was missed, write it on the next available line of the current book. A US marine survey guide (checked September 2026) gives this instruction. Do not squeeze it between existing lines, and do not start a fresh page to hide it.

Flag states differ on how they want a late entry endorsed. Where your flag's instructions or the ship's approved procedures are more specific, they take priority.

How inspectors reconcile the book with everything else

Reconciliation means laying the Part I entries next to every other record of the same oil and checking that they tell one story. The guides describe the process in general terms. On board it comes down to a handful of comparisons that can be run before any inspector arrives.

1. Soundings against the book. Take the sludge and bilge tank quantities from the sounding record and check that each Part I entry moves them the way the book says.
2. Oil monitoring record against OWS entries. The start and stop times in the book should match the times the monitor recorded, and the discharge should sit inside the positions written down.
3. Engine room log against Part I. The engine room log (ER log, the watchkeeping record engineers fill in every watch) should agree with the book. If the ER log shows the separator running at a time the Oil Record Book (ORB) does not mention, that gap will be found.
4. Receipts against disposal entries. Every sludge landing to a reception facility needs a receipt, and the receipt quantity should match the entry.
5. Bunker paperwork against bunkering entries. BDN quantities per grade should agree with the tanks and totals in the book.

Sludge quantities are where this usually falls apart, because they depend on how well the purifiers (the machines that spin water and sludge out of fuel and lube oil) are running. If sludge generation jumps without an obvious cause, look at the separators first, since a badly run purifier is the most common reason the numbers stop matching. Our fuel oil purifier troubleshooting guide covers what to inspect before the numbers drift further. Fuel figures need the same care. SFOC, or specific fuel oil consumption, is how much fuel the engine burns per unit of power it makes. It gives a second way to check whether tank movements add up. If consumption is already tracked closely, the method in how to calculate main engine SFOC and daily fuel consumption sets out the full calculation. Cross-checking against it can catch a fuel discrepancy before it becomes a question at the next inspection.

Which fields each Part I operation needs

The fields change with the operation, and this is the gap the published guides leave open. Use the list below as a working reminder, and check it against the item list printed for each code in your own book, because that is the version an inspector will hold you to.

• OWS discharge of bilge water: tank of origin, quantity, start and stop time, start and stop position, and confirmation the equipment ran as required.
• Sludge collection or disposal: tank identity, quantity retained or removed, disposal method, and the receipt reference where the sludge went ashore.
• Bunkering of fuel or bulk lube oil: port, start and stop time, grade, quantity added to each tank, and the total.
• Internal transfers: tank from, tank to, quantity moved, and the resulting quantity where the item asks for it.
• A missed operation: the full entry on the next available line, with signatures and any endorsement your flag requires.

For every line, the same final checks apply: correct code letter, correct item number, a narrative a stranger could follow, a signature, and no blank space left above it.

Hard copy or electronic record book: honest pros and cons

An electronic record book removes some of these errors and leaves others untouched. The IMO describes it, in resolution MEPC.314(74) (checked September 2026), as a system approved by the Administration and used in place of the hard-copy book. Approval by your flag Administration — the flag state's own maritime regulator — is the boundary. The research found nothing showing that any particular commercial product is approved for every flag or every vessel.

Here are the real strengths of a well-run electronic book:

• Mandatory fields make the half-entry harder to save.
• Code selection from a list cuts down on free-text code mistakes.
• Corrections can be forced into a traceable format, which ends white-out.

The cons are just as real:

• Approval is flag-specific. A system approved by one Administration does not automatically cover a ship under another flag.
• It does not reconcile your numbers. Soundings, monitor records and receipts still need a human to compare them.
• A dropdown can still be wrong. Picking Code D for a sludge transfer is as easy on a screen as on paper.
• Pricing and approval status are unclear from public sources. Nothing in the September 2026 research gave reliable current prices or approval lists, so this would mean relying on vendor quotes.

If you are building a wider digital kit for the engine room, our roundups of the best apps for marine engineers and the digital tools every chief engineer should know cover supporting software. Neither replaces the statutory book.

Who should not rush to an electronic record book

Ships that change flag often, or that run on a management company's paper SMS forms, gain little from switching before approval is settled. The same goes for any ship where the real problem is discipline, such as late entries and unsigned pages. Software will not fix a habit of writing up the book on Sunday night.

What may change in Part I recording

Changes are in progress, and they are not yet confirmed. An ABS regulatory brief on the IMO's Sub-Committee on Pollution Prevention and Response, at its 13th session (PPR 13), reports that the sub-committee agreed draft amendments and revised guidance for recording operations in Part I. The brief says these were aimed at approval at MEPC 84 — the 84th session of the IMO's Marine Environment Protection Committee — in April 2026, and adoption at MEPC 85 in November 2026. The research available on 29 September 2026 does not show whether MEPC 84 approved them. Watch your flag's circulars and your class society's regulatory news before the end of the year.

FAQ

How soon must an Oil Record Book Part I entry be made?

It must be made on completion of the operation or without delay. The Bahamas Maritime Authority notice, checked in September 2026, says the person directly responsible should make it. An inspection guide from the same period recommends two hours as best practice, which is a habit and not a legal deadline.

How do I correct a mistake in the Oil Record Book?

Draw a single thin line through the wrong entry so the original stays readable, then write the amendment, date it and sign it. Bahamas guidance, checked in September 2026, says necessary amendments should be made within 24 hours of the operation and endorsed by the Chief Engineer or Master and the responsible officer. Never use white-out.

What if I forgot to record an operation?

Enter it on the next available line of the current book as soon as you notice. A US marine survey guide, checked in September 2026, gives this instruction. Follow your flag's rules on how a late entry must be endorsed, because they vary.

Can Port State Control compare the book with the OWS monitor record?

Yes, they can. Liberian registry guidance from 2012, checked in September 2026, says inspectors may compare entries with the electronic record kept by oil monitoring equipment, and a mismatch can contribute to detention. Check your times and positions against the monitor before you sign.

Does an electronic record book replace the paper Oil Record Book?

It can, but only when your flag Administration has approved that system for your ship. The IMO describes it as an approved system used instead of the hard-copy book. Without that approval, the paper book is still the statutory record.

Verdict

Most Part I trouble comes from ordinary habits: writing the start of an operation and not the end, filing work under a neighbouring code, and tidying up errors in a way that hides them. The fixes are just as ordinary. Write on completion, use the full code and item, sign as you go, correct with a single line, and reconcile against soundings, monitor records and receipts before arrival.

Related reading

• MARPOL Annex VI fuel oil sampling and bunker delivery note checklist
• Fuel oil purifier troubleshooting for marine engineers
• Digital tools every chief engineer should know

About this guide

This guide is compiled from flag state notices, registry guidance and inspection guides, each named where it is used above. The claims list attached to this page records which source supports each figure, when it was checked, and when it should be checked again. Where a figure could not be confirmed against a primary regulation — the MARPOL Annex I text itself or an IMO circular — that gap is stated in the text above rather than filled in.

Latest updates

• CII Rating Explained: 6 Engine Room Changes (2026) — our newest guide on this topic.