VLSFO Marine Fuel Guide — IMO 2020, 0.5% Sulfur Bunker Fuel Explained
Everything ship operators, fuel traders and importers need to know about VLSFO (Very Low Sulfur Fuel Oil): what it is, how it relates to IMO 2020, how it compares with HSFO and MGO, typical specifications, and how to source VLSFO on FOB or CIF terms.
What is VLSFO?
VLSFO stands for Very Low Sulfur Fuel Oil. It is a category of marine bunker fuel with a maximum sulfur content of 0.50% mass/mass, used as the primary IMO 2020 compliant fuel for ocean-going vessels. VLSFO sits between traditional heavy fuel oil (HSFO, up to 3.5% sulfur) and marine gas oil (MGO, max 0.10% sulfur) in terms of both sulfur content and cost.
VLSFO is typically a blended product — refiners and bunker suppliers combine residual and distillate components to produce a fuel meeting the 0.5% sulfur limit while maintaining acceptable viscosity (typically 380–500 cSt at 50 °C) and other ISO 8217 parameters. The exact blend composition varies by refinery and region.
On a global basis, VLSFO became the dominant marine fuel grade after 1 January 2020, when the IMO 2020 regulation took effect. It is available at major bunkering hubs worldwide including Singapore, Rotterdam, Fujairah, Houston and at export terminals on the Black Sea.
IMO 2020 — the global sulfur cap
The IMO 2020 regulation — formally known as MARPOL Annex VI, Regulation 14 — took effect on 1 January 2020. It reduced the global limit for sulfur in marine fuels from 3.50% to 0.50% mass/mass. In designated Emission Control Areas (ECAs) — including the Baltic Sea, North Sea, North American coast and US Caribbean — the limit is even stricter at 0.10%.
The rationale is environmental: sulfur dioxide (SO₂) emissions from ships contribute to acid rain, respiratory health problems in coastal populations, and particulate matter pollution in port cities. The IMO estimates the regulation prevents over 570,000 premature deaths annually.
To comply with IMO 2020, ship operators had three main options:
- Switch to VLSFO — burn compliant low-sulfur fuel with max 0.50% sulfur. The most common solution adopted by the industry.
- Install exhaust gas scrubbers (EGS) — continue burning cheaper HSFO but capture sulfur in the scrubber before emission. Capital-intensive upfront but can pay back in fuel cost savings.
- Switch to LNG (liquefied natural gas) — new-build vessels designed for LNG propulsion. A long-term solution with near-zero sulfur emissions.
The majority of the global fleet chose VLSFO as the path of least resistance, driving a dramatic restructuring of the marine fuel market from late 2019 through 2020.
VLSFO vs HSFO vs MGO — key differences
| Parameter | HSFO (High Sulfur FO) | VLSFO (0.5% S) | MGO (Marine Gas Oil) |
|---|---|---|---|
| Max sulfur | 3.50% | 0.50% | 0.10% |
| IMO 2020 compliance | Only with scrubber | Yes (open sea) | Yes (all zones) |
| Viscosity (cSt at 50°C) | 380–700 | 380–500 | 1.5–11 (distillate) |
| ISO 8217 grade | RMG 380 / RMF 180 | RMG 380 (0.5%S blend) | DMB / DMA |
| Typical use | Deep sea (with EGS) | Deep sea (no EGS) | ECA zones, auxiliary engines |
| Relative cost | Lowest | Medium | Highest |
| Energy content | ~40.5 MJ/kg | ~40.2 MJ/kg | ~42.7 MJ/kg |
VLSFO offers a cost advantage over MGO of typically USD 80–150/MT depending on market conditions, making it the preferred IMO 2020 solution for most vessel operators on international routes. HSFO remains cheaper but requires scrubber investment (~USD 2–5 million per vessel).
VLSFO specification — ISO 8217
VLSFO is governed by ISO 8217 (Petroleum Products — Fuels for Marine Diesel Engines and Boilers). The key parameters for a typical VLSFO meeting the IMO 2020 sulfur limit are:
| Parameter | ISO 8217 Limit / Typical Value |
|---|---|
| Sulfur (max) | 0.50% m/m |
| Viscosity at 50 °C (max) | 380 cSt (RMG 380) or 500 cSt (RMG 500) |
| Density at 15 °C (max) | 991.0 kg/m³ |
| Flash point (min) | 60 °C |
| Pour point (max) | 30 °C (summer) / 0 °C (winter) |
| Water content (max) | 0.50% v/v |
| Ash (max) | 0.10% m/m |
| Vanadium (max) | 350 mg/kg |
| Aluminium + Silicon (max) | 60 mg/kg |
| Carbon residue (max) | 18% m/m |
Note: VLSFO is not a single standardised product — it is a performance category. Different blends can meet the same ISO 8217 limits with very different compositions, which has implications for stability and compatibility (see below).
VLSFO compatibility and stability — what buyers need to know
One of the key challenges with VLSFO is that, unlike the relatively homogeneous HSFO market of the pre-2020 era, VLSFO blends vary significantly by supplier and port. This creates two related risks:
Stability
Some VLSFO blends — particularly those with high aromatic content combined with paraffinic components — can be unstable and develop sludge or asphaltene precipitation in fuel tanks. This can clog filters and purifiers, damaging fuel system components. Buyers and ship operators should request a CCAI (Calculated Carbon Aromaticity Index) value and verify it is within acceptable limits (typically CCAI < 870 for VLSFO).
Compatibility
Mixing VLSFO from different suppliers can cause incompatibility — two individually stable fuels may destabilise when combined. Before topping up tanks, operators should check that the new VLSFO delivery is compatible with the remaining fuel using the ASTM D7112 blend compatibility test or by requesting blend compatibility certificates from the supplier.
We supply VLSFO with full CoA and quality certificates, and can provide CCAI data. Contact us before placing an order if you have specific stability requirements for your vessel or route.
How to buy VLSFO bunker fuel — supply terms FOB and CIF
Alghaf Marine DMCC supplies VLSFO meeting IMO 2020 and ISO 8217 from Russian refineries on the following terms:
- FOB Black Sea (Novorossiysk) — you nominate a vessel and take delivery at the port of loading. You arrange and pay for onward freight. This is the standard option for trading companies and ship operators with established freight relationships.
- CIF — Cost, Insurance, Freight — we deliver VLSFO to your destination port with freight and insurance included. One point of contact. Suitable for buyers who prefer turnkey delivery to a specific port.
To request VLSFO availability and pricing, provide:
- Volume required (metric tons)
- Delivery basis (FOB or CIF) and port
- Required delivery window or laycan
- Any specific ISO 8217 grade requirements or CCAI limits
Frequently Asked Questions About VLSFO
What is VLSFO?
VLSFO (Very Low Sulfur Fuel Oil) is a marine bunker fuel with a maximum sulfur content of 0.50% mass/mass, compliant with the IMO 2020 global sulfur cap. It is the most widely used IMO 2020 compliant fuel for ocean-going vessels that do not have exhaust gas scrubbers.
What does VLSFO stand for in shipping?
VLSFO stands for Very Low Sulfur Fuel Oil. In the bunkering and shipping industry it refers specifically to marine fuel with max 0.50% sulfur, meeting the IMO 2020 MARPOL Annex VI requirement. It is also called "0.5% fuel oil", "compliant bunkers" or "low sulfur residual fuel".
What is IMO 2020 and how does VLSFO relate to it?
IMO 2020 is the International Maritime Organization regulation (MARPOL Annex VI) that reduced the global sulfur limit for marine fuels from 3.5% to 0.50% from 1 January 2020. VLSFO is the main compliant fuel that allows ships to continue using residual fuel oil (more economical than MGO) while meeting this new sulfur limit.
What is the difference between VLSFO and HSFO?
HSFO (High Sulfur Fuel Oil) has up to 3.5% sulfur and is no longer compliant with IMO 2020 regulations unless the vessel has a scrubber. VLSFO has max 0.50% sulfur and is IMO 2020 compliant for use anywhere outside ECAs. HSFO is cheaper per ton but requires a scrubber investment of USD 2–5 million per vessel.
What is the viscosity of VLSFO?
VLSFO typically has a kinematic viscosity of 380 cSt at 50 °C (classified as RMG 380 under ISO 8217), though some blends are 180 cSt or 500 cSt. The viscosity determines how the fuel is handled and preheated on board. Standard VLSFO at 380 cSt requires preheating to approximately 100–120 °C for optimal atomisation in marine diesel engines.
How do I buy VLSFO from Alghaf Marine?
Contact us via Telegram @AlghafMarine_bot or email info@alghafmarine.com with your volume (MT), delivery port, and required delivery window. We supply VLSFO ISO 8217 compliant, FOB Black Sea or CIF to your port. We respond to all qualified inquiries within 24 business hours.
Related pages
VLSFO Product Page · RMG 380 Fuel Oil · Marine Gasoil · FOB vs CIF Logistics Guide · RMG 380 Bunker Fuel Guide
Alghaf Marine DMCC — petroleum products export. This article is for informational purposes. Pricing and commercial terms are provided upon request. © 2026 Alghaf Marine DMCC.