Virgin fuel oil D6 is a heavy residual fuel oil: the thick, dark oil left after lighter fuels have been distilled from crude. “Virgin” means it comes straight from distillation rather than being blended from recycled or re-refined oil. D6 is used mainly as a refinery feedstock and as fuel for industrial boilers and power plants.
This guide explains what D6 is, the parameters that define it, how it compares with similar fuels, and what to check before buying. For supply, see our virgin fuel oil D6 page.
What D6 is
When crude oil is distilled, lighter products such as gasoline, jet fuel and diesel boil off first. The heavy fraction that remains is residual fuel oil. In US terminology, the heaviest commercial grade is No. 6 fuel oil, also known as residual or bunker C fuel. “D6” is the name widely used in international trade for heavy residual fuel oil of this type.
Because it is very viscous, D6 must be heated to be stored, pumped and burned. It is cheaper per tonne than distillate fuels, but it needs suitable equipment.
Typical specification parameters
D6 cargoes are defined by a contract specification, not a single international standard. The main parameters are:
| Parameter | Why it matters |
|---|---|
| Density at 15 C | Heavy fuel; affects handling, blending and value |
| Kinematic viscosity | The key property for heating, pumping and atomising |
| Sulphur content | Varies widely by crude source; determines emission compliance |
| Flash point | Safety in storage and handling |
| Pour point | Temperature at which it stops flowing |
| Water and sediment | Reduce heating value and cause equipment problems |
| Ash and metals (vanadium, nickel) | Cause deposits and corrosion |
| Calorific value | Energy content per kilogram |
For reference, the US standard ASTM D396 defines Grade No. 6 fuel oil mainly by a kinematic viscosity at 100 C of 15 to 50 mm2/s, a minimum flash point of 60 C and a maximum of 2% water and sediment. Commercial D6 offers often state additional limits for density, sulphur and metals.
D6 compared with similar fuels
| Fuel | What it is |
|---|---|
| D6 / No. 6 fuel oil | Heavy residual fuel oil, used as refinery feedstock and industrial fuel |
| D2 / gasoil / diesel | Light distillate fuel; see EN590 diesel |
| Heavy fuel oil (HFO) for ships | Residual marine fuel sold to ISO 8217 grades, now limited to 0.5% sulphur outside emission control areas unless ships use scrubbers |
| Mazut | A heavy residual fuel oil term used in Russia and Central Asia |
Uses
- Refinery feedstock: refineries with cracking or coking units convert residual oil into lighter, more valuable products. Much traded D6 goes to refiners.
- Industrial boilers and furnaces: steam and heat for heavy industry.
- Power generation: in plants equipped to burn residual fuel.
- Marine fuel: as a blending component for residual bunker fuels, within sulphur rules.
Checks before buying D6
- Specification and test methods agreed in the contract.
- Independent inspection of quality and quantity at the loading terminal.
- Verification of the seller and the product: company registration, terminal and storage confirmation directly with the terminal, and proof of title.
- Sanctions and origin compliance for the crude source and route.
- No upfront fees: be cautious of any request to pay fees before the product is verified. The fuel oil market has many unverifiable offers; our guide to TTT and TTM procedures explains safe steps.
D6 from Agromer
Agromer offers US-origin virgin fuel oil D6 to corporate direct buyers with an LOI only, on an FOB TTT procedure. Send a recent LOI on company letterhead with quantity, specification, delivery period and destination.
Frequently asked questions
What is virgin fuel oil D6?
A heavy residual fuel oil taken straight from crude distillation, rather than blended from recycled oil. It is similar to No. 6 fuel oil.
What is D6 used for?
Mainly as a refinery feedstock and as fuel for industrial boilers and power plants.
What is the difference between D2 and D6?
D2 is a light distillate fuel similar to diesel. D6 is a heavy residual fuel oil that must be heated before use.
Is D6 the same as bunker fuel?
They are related. Residual fuels like D6 are used to make marine heavy fuel oil, but ships buy to ISO 8217 marine grades and sulphur limits.
What does “virgin” mean in virgin fuel oil?
That the oil comes directly from refining crude oil, not from recycled or re-refined used oil.
Why must D6 be heated?
It is very viscous at normal temperatures, so it needs heating to flow through pipes and to atomise properly in burners.