Marine fuel reference · Reviewed September 6, 2026
Fuel Oil Specifications
MGO, MDO and HFO describe fuel families. A usable specification also identifies the ISO grade, standard edition, test conditions and supplier’s certificate of quality.
Use this guide to check the information accompanying a fuel offer. Numerical acceptance limits must come from the contracted standard and grade; a generic range is not a certificate for a delivered batch.
ISO fuel quality and sulfur requirements
ISO 8217:2024 defines marine-fuel quality requirements. Identify the edition agreed with the supplier; a newer edition does not automatically change an existing contract.
The IMO sulfur guidance explains the 0.50% mass/mass global fuel-sulfur limit and 0.10% limit in sulfur emission control areas. Approved equivalent compliance arrangements can apply. These emissions requirements are separate from a complete ISO grade specification; confirm the rules for the vessel and voyage.
Marine Gas Oil (MGO)
A marine distillate fuel. The commercial name alone does not establish the contracted ISO grade or sulfur content.
Grade and standard
Request the declared distillate grade, such as DMA, and the edition of ISO 8217 in the contract.
Supplier checks
Confirm density at the stated temperature, viscosity and test temperature, flash point, cold-flow properties and sulfur test result.
Marine Diesel Oil (MDO)
A commercial description whose composition depends on the supplied product. Do not infer suitability or composition from the name alone.
Grade and standard
Ask the supplier to identify the exact ISO grade; verify any residual or bio-component content against that grade and your equipment requirements.
Supplier checks
Check the certificate of quality, fuel handling requirements, stability and compatibility with fuel already on board.
Heavy Fuel Oil (HFO)
A residual marine fuel category, with different viscosity grades and sulfur contents. HFO is not inherently a 0.50% sulfur product.
Grade and standard
Record the full residual-grade designation and standard edition, not only a commercial viscosity label such as 380.
Supplier checks
Verify viscosity at its test temperature, density, water, sediment, stability and contaminants against the purchased grade and engine requirements.
Compare specifications on the same basis
| Property | What to verify |
|---|---|
| Density | Record kg/m³ and the reference temperature; do not convert a mass quote to volume using an assumed density. |
| Viscosity | Record mm²/s (cSt) and test temperature. Values at 40°C and 50°C are not interchangeable. |
| Sulfur | Record measured % mass/mass and verify the applicable vessel, voyage and compliance requirements. |
| Flash point and cold flow | Check the test method, grade limits and operating conditions with the supplier and equipment guidance. |
| Quality documentation | Keep the named grade, ISO edition, certificate of quality, sampling information and bunker delivery documentation together. |
| Price comparison | Match the port, grade, currency, unit, observation date and delivery terms before comparing prices. |
Use marine price data in your workflow
OilPriceAPI provides price benchmarks. A price observation does not certify the quality of a delivered fuel batch. Obtain specifications and quality documentation from the supplier; use the API documentation to confirm supported ports, grades and access.