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Fuel Oil

Fuel oil is a fraction obtained from petroleum distillation, either as a distillate or a residue. Broadly speaking fuel oil is any liquid petroleum product that is burned in a furnace or boiler for the generation of heat or used in an engine for the generation of power, except oils having a flash point of approximately 40 °C (104 °F).  Fuel oil is made of longhydrocarbon chains, particularly alkanes, cycloalkanes and aromatics. different organizations may have different numerical specifications for the six fuel oil grades. The boiling point and carbon chain length of the fuel increases with fuel oil number. Viscosity also increases with number.


Fuel Oil


Category Product    
  180 CST    
Fuel Oil 280 CST    
  380 CST    


Mazut is a heavy, low quality fuel oil, used in power plants and similar applications. In the United States and Western Europe, mazut is blended or broken down, with the end product being diesel.

Mazut may be used for heating houses in the former USSR and in countries of the Far East that do not have the facilities to blend or break it down into more conventional petro-chemicals. In the West, furnaces that burn mazut are commonly called "waste oil" heaters or "waste oil" furnaces.

Mazut-100 is a fuel oil that is manufactured to GOST specifications, for example GOST 10585-75 (not active) or GOST 10585-2013 (active as per December 2019. Mazut is almost exclusively manufactured in the Russian Federation, Kazakhstan, Azerbaijan, and Turkmenistan.This product is typically used for larger boilers in producing steam since the energy value is high.

The most important factor when grading this fuel is the sulfur content, which can mostly be affected by the source feedstock. For shipment purposes, this product is considered a ”dirty oil” product, and because viscosity drastically affects whether it is able to be pumped, shipping has unique requirements. Mazut is much like Number 6 Oil (Bunker C), and is part of the products left over after gasoline and lighter components are evaporated from the crude oil.


The main difference between the different types of Mazut-100 is the content of sulphur. The grades are represented by these sulfuric levels:

”Very Low Sulphur” is mazut with a sulphur content of 0.5%
”Low Sulphur” is a mazut with a sulphur content of 0.5-1.0%
”Normal Sulphur” is a mazut with a sulphur content of 1.0-2.0%
”High Sulphur” is a mazut with a sulphur content of 2.0-3.5%
Very Low Sulphur mazut is generally made from the lowest sulfur crude feedstocks. It has a very limited volume to be exported because:

The number of producers in Russia is limited. Refineries which produce this are generally owned by the largest domestic oil companies, such as Lukoil and Rosneft, etc.
In Russia and the CIS a minimum of 50% from the total produced volume is sold only to domestic consumers in Russia and the CIS.
Most of the remainder amount is reserved by state quotas for state controlled companies abroad.
The remaining volume available for export is sold according to state quotas, via state auctions, accessible only to Russian domestic companies.
Low to high sulfur mazut is available from Russia and other CIS countries (Kazakhstan, Azerbaijan, Turkmenistan). The technical specifications are represented in the same way, according to the Russian GOST standard 10585-99. The Russian origin mazut demands higher prices.


Class C1 and C2 fuels are kerosene-type fuels. C1 is for use in flueless appliances (e.g. lamps). C2 is for vaporising or atomising burners in appliances connected to flues.

Class A2 fuel is suitable for mobile, off-road applications that are required to use a sulphur-free fuel. Class D fuel is similar to Class A2 and is suitable for use in stationary applications, such as domestic, commercial, and industrial heating. The BS 2869 standard permits Class A2 and Class D fuel to contain up to 7% (V/V) biodiesel (fatty acid methyl ester, FAME), provided the FAME content meets the requirements of the BS EN 14214 standard.

Classes E to H are residual oils for atomizing burners serving boilers or, with the exception of Class H, certain types of larger combustion engines. Classes F to H invariably require heating prior to use; Class E fuel may require preheating, depending on ambient conditions.



Mazut is a residual fuel oil often derived from Russian petroleum sources and is either blended with lighter petroleum fractions or burned directly in specialized boilers and furnaces. It is also used as a petrochemical feedstock. In the Russian practice, though, "mazut" is an umbrella term roughly synonymous with the fuel oil in general, that covers most of the types mentioned above, except US grades 1 and 2/3, for which separate terms exist (kerosene and diesel fuel/solar oil respectively — Russian practice doesn't differentiate between diesel fuel and heating oil). This is further separated in two grades, "naval mazut" being analogous to US grades 4 and 5, and "furnace mazut", a heaviest residual fraction of the crude, almost exactly corresponding to US Number 6 fuel oil and further graded by viscosity and sulphur content.


Maritime fuel classification

In the maritime field another type of classification is used for fuel oils:

· MGO (Marine gas oil) - roughly equivalent to No. 2 fuel oil, made from distillate only

· MDO (Marine diesel oil) - A blend of heavy gasoil that may contain very small amounts of black refinery feed stocks, but has a low viscosity up to 12 cSt so it need not be heated for use in internal combustion engines

· IFO (Intermediate fuel oil) A blend of gasoil and heavy fuel oil, with less gasoil than marine diesel oil

· MFO (Marine fuel oil) - same as HFO (just another "naming")

· HFO (Heavy fuel oil) - Pure or nearly pure residual oil, roughly equivalent to No. 6 fuel oil

Marine diesel oil contains some heavy fuel oil, unlike regular diesels.


Standards and classification

CCAI and CII are two indexes which describe the ignition quality of residual fuel oil, and CCAI is especially often calculated for marine fuels. Despite this, marine fuels are still quoted on the international bunker markets with their maximum viscosity (which is set by the ISO 8217 standard - see below) due to the fact that marine engines are designed to use different viscosities of fuel. The unit of viscosity used is the centistoke (cSt) and the fuels most frequently quoted are listed below in order of cost, the least expensive first.

· IFO 380 - Intermediate fuel oil with a maximum viscosity of 380 centistokes (<3.5% sulphur)

· IFO 180 - Intermediate fuel oil with a maximum viscosity of 180 centistokes (<3.5% sulphur)

· LS 380 - Low-sulphur (<1.0%) intermediate fuel oil with a maximum viscosity of 380 centistokes

· LS 180 - Low-sulphur (<1.0%) intermediate fuel oil with a maximum viscosity of 180 centistokes

· MDO - Marine diesel oil.

· MGO - Marine gasoil.

· LSMGO - Low-sulphur (<0.1%) Marine Gas Oil - The fuel is to be used in EU Ports and Anchorages. EU Sulphur directive 2005/33/EC

· ULSMGO - Ultra-Low-Sulphur Marine Gas Oil - referred to as Ultra-Low-Sulfur Diesel (sulphur 0.0015% max) in the US and Auto Gas Oil (sulphur 0.001% max) in the EU. Maximum sulphur allowable in US territories and territorial waters (inland, marine and automotive) and in the EU for inland use.

The density is also an important parameter for fuel oils since marine fuels are purified before use to remove water and dirt from the oil. Since the purifiers use centrifugal force, the oil must have a density which is sufficiently different from water. Older purifiers work with a fuel having a maximum of 991 kg/m3; with modern purifiers it is also possible to purify oil with a density of 1010 kg/m3.

The first British standard for fuel oil came in 1982. The latest standard is ISO 8217 issued in 2017. The ISO standard describe four qualities of distillate fuels and 10 qualities of residual fuels. Over the years the standards have become stricter on environmentally important parameters such as sulfur content. The latest standard also banned the adding of used lubricating oil (ULO).

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