Short answer: VLSFO contains no more than 0.50% sulphur and can be used by any ship under the MARPOL Annex VI global limit. HSFO contains up to 3.50% sulphur and can only be used by ships with an approved exhaust gas cleaning system (scrubber). Both are residual fuels, usually bought at the 380 cSt viscosity grade, and the number 380 says nothing about sulphur.
Two different properties: sulphur and viscosity
The most common source of confusion is the label. “380” refers to viscosity: a maximum of 380 mm²/s (cSt) at 50°C, typically ISO 8217 grade RMG 380. “High sulphur” or “very low sulphur” refers to sulphur content. So a VLSFO 380 and an HSFO 380 have the same viscosity grade but different sulphur classifications.
| VLSFO | HSFO | |
|---|---|---|
| Sulphur | ≤ 0.50% m/m | up to 3.50% m/m |
| Who can burn it | Any ship outside ECAs | Only ships with an approved scrubber |
| Typical grade | RMG 380 (also RME 180, RMD 80) | RMG 380 (also 180) |
| Composition | Varies widely by blend | More consistent, traditional residual |
| Main handling issues | Stability, compatibility, cold flow | Heating, cat fines, sludge |
| Price | Usually higher | Usually a discount to VLSFO |
Why VLSFO exists
On 1 January 2020 the MARPOL Annex VI global sulphur limit for marine fuel fell from 3.50% to 0.50%. Refiners responded with new blends that meet 0.50%: mixtures of low sulphur residues, hydrotreated components, cracked stocks and distillates. These became VLSFO. Because recipes differ, VLSFO properties vary from one delivery to the next far more than HSFO did.
Why HSFO is still bought
Ships fitted with scrubbers can keep burning HSFO, because the scrubber removes sulphur oxides from the exhaust to an equivalent level. The price spread between HSFO and VLSFO is what pays for the scrubber. Since 1 March 2020, ships without an approved scrubber may not even carry HSFO for use on board.
Operational differences
VLSFO
- Compatibility: two compliant VLSFOs can be incompatible and form sludge when mixed. Segregate deliveries.
- Stability: some blends are close to their stability limits. Check total sediment results.
- Cold flow: paraffinic blends can have high pour points, so plan tank heating.
HSFO
- Heating: requires heating for transfer, purification and injection.
- Cat fines and sludge: purifier set-up and monitoring are essential.
- Scrubber rules: in Singapore, open-loop scrubber washwater discharge is not permitted in port waters, so open-loop systems must switch to closed loop or compliant fuel in port.
Procurement implications
- Always state both sulphur and viscosity: “VLSFO RMG 380, S max 0.50%” or “HSFO RMG 380, S max 3.50%”.
- State the ISO 8217 edition.
- For scrubber ships, consider carrying compliant fuel for scrubber downtime and port operation.
- Arrange independent testing of new VLSFO stems before use, particularly stability and compatibility.
See our VLSFO and HSFO 380 pages for Singapore supply details.
Frequently asked questions
Is VLSFO the same as LSFO?
In current usage, VLSFO means fuel with no more than 0.50% sulphur. LSFO is an older, looser term and has been used for fuels at 1.00% sulphur or below, so it is better to state the sulphur limit precisely.
Can a ship switch between HSFO and VLSFO?
A scrubber-fitted ship can use either. Mixing the two in the same tank should be avoided because of compatibility risk.