Product overview
Residual fuel oil is produced from the bottom of the refining process and is characterised chiefly by viscosity, density and sulphur content. Viscosity grades such as 380 CST and 180 CST describe how the oil flows at 50 °C and therefore how it must be heated and handled.
Since the global marine sulphur limit took effect, the market has centred on VLSFO at a maximum 0.50% sulphur for vessels without scrubbers, alongside HSFO for vessels fitted with exhaust gas cleaning systems. Marine residual fuels are specified under ISO 8217.
Typical specifications
| Reference standard | ISO 8217 (marine residual fuels) |
|---|---|
| Kinematic viscosity at 50 °C | 380 cSt max (RMG 380 grade) |
| Density at 15 °C | 991.0 kg/m³ max |
| Sulphur — VLSFO | 0.50% by mass max |
| Sulphur — HSFO | up to 3.5% by mass |
| Flash point | 60 °C min |
| Pour point | grade and season dependent |
| Water content | 0.5% by volume max |
Indicative typical values shown for orientation only. Exact quality is cargo-dependent and the final contractual specification, as confirmed in the sales agreement and verified by independent inspection, prevails.
Commercial relevance and typical uses
The largest outlet for residual fuel oil is marine bunkering, where it powers large two-stroke and four-stroke engines. It is also burned in power generation, industrial boilers and process heating, and feeds some refinery and upgrading units.
Grade choice follows the vessel or plant: VLSFO where emissions must meet the 0.50% limit without abatement, and HSFO where a scrubber is installed. Viscosity determines the heating and pumping arrangements required at the receiving facility.
Quality and independent inspection
Fuel oil is sampled and tested by an independent inspector against the agreed viscosity, density, sulphur and stability limits, with a certificate of quality issued at load. Compatibility and stability matter because residual fuels from different sources can interact, so representative sampling is important. 3FB coordinates inspection; SGS and Intertek are cited only as examples of firms active in the sector, not as partners.
Sealed retention samples are usually kept for later reference. See how independent inspection works and inspection.
Shipping and logistics
Fuel oil moves in dirty petroleum product and residual tankers with heating coils, and is delivered to shore tanks or, for bunkers, by barge. 3FB trades on FOB terms, where the buyer lifts at the load port, and on CIF terms, where 3FB arranges freight and insurance to discharge, as described in FOB versus CIF.
Delivery is scheduled against an agreed laycan, and heating during carriage is planned to keep the cargo pumpable. See shipping and logistics.
Trade documentation
A fuel oil cargo carries the bill of lading, certificate of origin, certificate of quality and certificate of quantity from the inspector, and the commercial invoice, with payment commonly under a documentary letter of credit against documents.
See the bill of lading and letter of credit explainers.
Buyer inquiry process
To request an indication, specify the grade (for example 380 CST, VLSFO or HSFO), the maximum sulphur, the volume, the delivery terms (FOB or CIF with the port), the laycan and the payment instrument. The desk assesses feasibility and responds with an indicative offer, subject to confirmation.
KYC and compliance review precede any definitive agreement. Begin at the trading desk.