Marine Fuel Management
How ships measure and use fuel data for speed, maintenance, bunkering and compliance.
Marine fuel management means measuring the fuel a ship uses by engine and voyage leg, and using that data for decisions on speed, maintenance, bunkering and compliance. Fuel is one of a ship's largest operating costs, so the subject was long treated purely as a cost question. Today the same data also sets the IMO carbon intensity rating and the emissions bill in the EU.
One distinction is worth making first. MFM is sometimes used as an abbreviation for marine fuel management, but in the bunker market it almost always means a mass flow meter. Spelling it out in contracts and correspondence avoids confusion.
The Basic Data
Fuel management rests on three questions: how much fuel was burned, what is left in the tanks, and what came on or went off. In a well-built system the consumption of each main engine and generator is visible from the bridge, and tank levels are tracked continuously. A sounding taken once or a few times a day comes late and misses small differences.
Transfer lines are a separate matter. Fuel loss and theft remain real problems in some regions. The way to see them is to fit flow meters on transfer lines and compare the figures with burn data. Once data is tied to voyage legs, the operator can also work out voyage cost from actual consumption.
Speed and Fuel Consumption
Slowing down usually saves fuel, but the relationship is less tidy than textbooks suggest. The common assumption is that consumption varies with the cube of speed. A 2020 empirical study of a tanker fleet by Adland and colleagues found that this holds only near design speed, and that sensitivity falls markedly at the speeds ships actually sail.[1] Clarksons also reports that the curve is flatter than the cube law at low speeds and that the effect can reverse below 9 to 10 knots.[2]
Engine revolutions alone are not a sufficient guide either. Wind, current, hull and propeller fouling, load and trim can produce very different consumption at the same revolutions. Comparisons are therefore made between voyages in similar load and weather conditions. ISO 19030 sets out how to measure the change in hull and propeller performance over time.
Maintenance and Bunkering
With real consumption and running hours, a maintenance schedule can follow the conditions an engine has actually seen. A slow rise in consumption on one engine is often the first sign of a fault.
Bunkering is an often neglected part of fuel management. The quantity received is recorded on the bunker delivery note (BDN), kept on board for three years under MARPOL Annex VI Regulation 18, and the sealed MARPOL sample is kept for at least 12 months.[3] Tracking the gap between the BDN and tank measurements shows at which port or supply a deviation arises. More detail is on the Fuel Oil and Gas Oil and Bunker Trading pages.
Fuel Data in Regulation
Finance, environment and compliance teams now look at the same table, because consumption figures are reported and verified directly.
| Regulation | Scope | Use of fuel data |
|---|---|---|
| IMO DCS | 5,000 GT and above | Since 1 January 2026 collected by consumer group and split between at sea and not at sea. 2026 data is verified by 31 March 2027. |
| CII and SEEMP | Ships in IMO scope | Annual carbon intensity rating. The reduction factor against 2019 is 13.625% in 2027, 16.25% in 2028, 18.875% in 2029 and 21.5% in 2030. |
| EU ETS | EU voyages, 5,000 GT and above | Allowances covered 70% of 2025 emissions; the share is 100% for 2026. Methane and N₂O have been in scope since 2026. |
| FuelEU Maritime | EU voyages, 5,000 GT and above | The greenhouse gas intensity limit is 2% lower in 2025 and 6% lower in 2030. A deficit is penalised at EUR 2,400 per tonne of VLSFO equivalent. |
Sources: IMO meeting summaries, Clyde & Co, UK P&I and the European Commission.[3][4][5][6]
Under FuelEU, all energy on voyages between EU ports and at berth counts, and half on voyages to or from outside the EU. A balance can be banked or pooled with another ship, and consumption data shows which is cheaper.[6] IMO's Net-Zero Framework, which would price carbon globally, has not been adopted as of 3 November 2026.[4] Emission values by fuel are compared in the guide to types of marine fuel.
Getting Started
On a ship with no system, the first step is a reliable noon report: the same hour, the same method, read tank by tank. Flow meters come next. Because meters also have errors, comparison with tank levels continues. Once the data is clean enough, speed decisions, maintenance plans and compliance reports all draw on one source. The effect of an investment such as new hull paint or an energy-saving device can only be measured against this baseline.
Frequently asked questions
What is marine fuel management?
Marine fuel management means measuring the fuel a ship uses by engine and voyage leg, and using that data for decisions on speed, maintenance, bunkering and compliance.
Do small vessels need fuel management?
The threshold for DCS, ETS and FuelEU is 5,000 GT, so small vessels fall outside them. Cost still matters, and a simple flow meter is often enough.
What happens with a low CII rating?
A ship rated D for three years in a row or E for one year submits a corrective action plan showing how it will reach at least a C.[7]
Sources
- Adland, R. et al. Norwegian School of Economics (NHH), study of speed and fuel consumption in a tanker fleet, 2020.
- Clarksons data, MarineLink: Savings from Speed Slow, 2024.
- Clyde & Co. MARPOL Annex VI: Key Developments for 2026; MARPOL Annex VI, Regulation 18.
- International Maritime Organization (IMO). Meeting summaries of MEPC 83 and MEPC 84; DNV. IMO MEPC 84: Revisiting the Net-Zero Framework, 2026.
- UK P&I Club. EU ETS and Shipping from 1 January 2026.
- European Commission. Guidance on the FuelEU Maritime Regulation, 2025; Regulation (EU) 2023/1805.
- International Maritime Organization (IMO). EEXI and CII: Frequently Asked Questions.
