RMG 380 Bunker Fuel Guide — Specification, Grades and How to Buy
Everything you need to know about RMG 380 marine fuel oil: what ISO 8217 Grade RMG 380 means, its viscosity and sulfur parameters, how it compares with VLSFO and MGO, and how to source RMG 380 on FOB or CIF terms.
What is RMG 380?
RMG 380 is a grade designation under ISO 8217 for marine residual fuel oil with a maximum kinematic viscosity of 380 centistokes (cSt) at 50 °C. It is one of the most widely traded bunker fuel grades globally and has been the dominant fuel for deep-sea vessel main engines for decades.
The name breaks down as follows:
- R — Residual (as opposed to D = distillate/gas oil)
- M — Marine fuel oil
- G — Grade Group G (ISO 8217 classification)
- 380 — Maximum kinematic viscosity: 380 cSt at 50 °C
RMG 380 is produced from the residual fractions of crude oil distillation — the heaviest material remaining after lighter products (naphtha, distillates) are extracted. It has a dark brown to black colour and high viscosity at ambient temperatures, requiring preheating before use.
Since IMO 2020, standard RMG 380 (with up to 3.5% sulfur — also called HSFO) can only be burned on vessels equipped with exhaust gas scrubbers (EGS). Without a scrubber, vessels must use VLSFO (low-sulfur variant, max 0.50% S) or MGO. Alghaf Marine supplies both HSFO RMG 380 and low-sulfur variants.
ISO 8217 — the marine fuel standard
ISO 8217 (Petroleum products — Fuels for marine diesel engines and boilers) is the primary international standard defining quality requirements for marine fuels. It classifies marine fuels into two families:
- Distillate grades (D) — lighter, lower viscosity fuels: DMA, DMB, DMC, DMX. Includes marine gas oil (MGO) and marine diesel oil (MDO).
- Residual grades (R) — heavier, higher viscosity fuels: RMA 10, RMB 30, RMD 80, RME 180, RMG 380, RMG 500, RMK 700. RMG 380 is the most commonly traded grade.
The current version is ISO 8217:2017. It specifies limits for viscosity, density, flash point, pour point, sulfur, water, ash, vanadium, aluminium + silicon, carbon residue, acid number and other parameters. Compliance is verified via Certificate of Analysis (CoA) issued by the refinery or supplier.
RMG 380 full specification — ISO 8217
| Parameter | ISO 8217 Limit (RMG 380) |
|---|---|
| Kinematic viscosity at 50 °C (max) | 380 cSt |
| Density at 15 °C (max) | 991.0 kg/m³ |
| Sulfur (max) | 3.50% m/m (HSFO) / 0.50% m/m (VLSFO) |
| Flash point (min) | 60 °C |
| Pour point (max) — summer zone | 30 °C |
| Pour point (max) — winter zone | 0 °C |
| Carbon residue (max) | 18% m/m |
| Ash (max) | 0.10% m/m |
| Water (max) | 0.50% v/v |
| Vanadium (max) | 350 mg/kg |
| Sodium (max) | 100 mg/kg |
| Aluminium + Silicon (max) | 60 mg/kg |
| Acid number (max) | 2.5 mg KOH/g |
| Hydrogen sulfide (max) | 2.00 mg/kg |
Actual delivered values typically come in well below the ISO 8217 limits for most parameters. The sulfur limit is critical for IMO 2020 compliance — a CoA must confirm the actual sulfur content before bunkering.
RMG 380 vs VLSFO vs MGO — comparison
| Parameter | RMG 380 (HSFO) | VLSFO (0.5%S) | MGO (DMB/DMA) |
|---|---|---|---|
| Max sulfur | 3.50% | 0.50% | 0.10% |
| Viscosity at 50 °C | 380 cSt | 180–380 cSt | 1.5–11 cSt |
| IMO 2020 compliant | Only with scrubber | Yes (open sea) | Yes (all zones) |
| Preheating required | Yes (~100–130 °C) | Yes (~100–120 °C) | No |
| Energy content | ~40.5 MJ/kg | ~40.2 MJ/kg | ~42.7 MJ/kg |
| Typical cost | Lowest | Medium | Highest |
| Primary users | Scrubber-equipped vessels | Deep-sea without scrubber | ECA zones, small vessels |
RMG 380 on board — heating, purification and handling
Due to its high viscosity, RMG 380 requires careful thermal management on board:
- Storage temperature: RMG 380 must be stored at sufficient temperature to remain pumpable — typically 40–50 °C above the pour point, usually 45–60 °C in storage tanks.
- Heating for injection: Before entering the fuel injection system, RMG 380 is heated to approximately 120–130 °C to reduce viscosity to the optimal injection range of 10–15 cSt.
- Purification: Heavy fuel oil contains sediments, water and catalytic fines. Two-stage centrifugal separators (purifiers and clarifiers) remove water and fine particles (Al+Si catalytic fines are particularly abrasive and must be reduced to <15 mg/kg before injection).
- HSFO/VLSFO changeover: When switching between HSFO RMG 380 and VLSFO, the fuel system must be carefully managed to ensure complete changeover and avoid mixing incompatible fuels.
Proper handling and maintenance of the fuel management system is critical to engine reliability when burning residual fuel oils such as RMG 380.
How to buy RMG 380 marine fuel oil — FOB and CIF supply
Alghaf Marine DMCC supplies RMG 380 meeting ISO 8217 with full CoA and BL documentation:
- FOB Black Sea (Novorossiysk) — delivery at the loading port. Buyer nominates vessel and takes cost and risk from the port of loading. Standard for marine fuel traders and operators with their own tanker fleet.
- CIF — Cost, Insurance, Freight — we deliver to your destination port with freight and insurance included. Suitable for buyers who need turnkey delivery to a specific port.
To request RMG 380 availability and pricing, provide:
- Volume (metric tons)
- Grade — HSFO (3.5% S max) or low-sulfur variant (0.5% S max)
- Delivery basis: FOB Black Sea or CIF (destination port)
- Required loading or delivery window
Frequently Asked Questions About RMG 380
What is RMG 380?
RMG 380 is a grade of marine residual fuel oil defined by ISO 8217, with a maximum kinematic viscosity of 380 cSt at 50 °C. It is one of the most widely used marine bunker fuel grades for deep-sea vessel main engines. Standard (HSFO) RMG 380 has up to 3.5% sulfur; low-sulfur variants (VLSFO) have max 0.50% sulfur for IMO 2020 compliance.
What does RMG 380 stand for?
RMG 380 stands for Residual Marine fuel oil, Grade Group G, with a maximum viscosity of 380 cSt at 50 °C. The ISO 8217 naming system uses R = Residual, M = Marine, G = Grade Group G (the highest viscosity group in the R series for most applications), and the number indicates the viscosity limit in centistokes.
What is the sulfur content of RMG 380?
Standard RMG 380 (HSFO) has a maximum sulfur content of 3.50% m/m per ISO 8217. Since IMO 2020, this is only compliant on vessels with exhaust gas scrubbers. Low-sulfur RMG 380 (VLSFO) variants with max 0.50% sulfur are IMO 2020 compliant without a scrubber. Our CoA confirms the actual sulfur value for each shipment.
What is the difference between RMG 380 and VLSFO?
Both can be at 380 cSt viscosity, but the key difference is sulfur content. RMG 380 (HSFO) has up to 3.5% sulfur and requires a scrubber for IMO 2020 compliance. VLSFO has max 0.50% sulfur and is IMO 2020 compliant without a scrubber. VLSFO typically costs more per ton than HSFO RMG 380 but avoids the capital cost of scrubber installation.
What temperature does RMG 380 need to be heated to?
RMG 380 should be stored at 45–60 °C to remain pumpable. Before fuel injection, it must be heated to approximately 120–130 °C to reduce viscosity to the optimal range of 10–15 cSt for atomisation in marine diesel engines. The exact temperature depends on the fuel's actual viscosity and the engine's injection system specifications.
How do I buy RMG 380 from Alghaf Marine?
Contact us via Telegram @AlghafMarine_bot or email info@alghafmarine.com with your volume (MT), grade (HSFO or low-sulfur), delivery port, and required delivery window. We supply RMG 380 ISO 8217 with full CoA and B/L documentation. We respond to qualified inquiries within 24 business hours.
Related pages
RMG 380 Product Page · VLSFO Marine Fuel · Marine Gasoil · VLSFO Guide · FOB vs CIF Logistics 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.