D6 is also be known as Residual Fuel Oil and is of high-viscosity. This particular fuel oil requires preheating to 220 260 Degrees Fahrenheit. D6 is mostly used for generators.

D6 is a type of residual fuel, mainly used in power plants and larger ships. The fuel requires to be preheated before it can be used. It is not possible to use it in smaller engines or vessels/vehicles where it is not possible to pre-heat it. D6 is its name in the USA. In other parts of the world it has other names.

Residual means the material remaining after the more valuable cuts of crude oil have boiled off. The residue may contain various undesirable impurities including 2 percent water and one-half percent mineral soil. D6 fuel is also known as residual fuel oil (RFO), by the Navy specification of Bunker C, or by the Pacific Specification of PS-400

Recent changes in fuel quality regulation now require further refining of the D6 in order to remove the sulfur, which leads to a higher cost. Despite this recent change, D6 is still less useful because of its viscosity as well as that it needs to be pre-heated before it can be used and contains high amounts of pollutants, such as sulfur. Since it requires pre-heating, it cannot be used in small ships or boats or cars. However large ships and power plants can use the residual fuel oil.
The price of D6 diesel traditionally rises during colder months as demand for heating oil rises, which is refined in much the same way.In many parts of the United States and throughout the United Kingdom and Australia, d6 diesel may be priced higher than petrol.

D6 Diesel 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 and the d6 fuel most frequently quoted are listed below in order of cost, the least expensive first-

* IFO 380  Intermediate d6 fuel oil with a maximum viscosity of 380 Centistokes
* IFO 180  Intermediate d6 fuel oil with a maximum viscosity of 180 Centistokes
* LS 380  Low-sulphur (< 1.5%) intermediate d6 fuel oil with a maximum viscosity of 380 Centistokes
* LS 180  Low-sulphur (< 1.5%) intermediate d6 fuel oil with a maximum viscosity of 180 Centistokes
* MDO  Marine diesel oil.
* MGO  Marine gasoil.