Bitumen is a low-grade of crude oil which is composed of complex, heavy hydrocarbons. In an oil reservoir, bitumen is a thick, viscous fluid and must be extracted from the ground. When extracting it, a lot of heat and effort must be used to upgrade it to a better product. Although bitumen is hard to extract from the ground, it can bubble naturally to the surface of the Earth in petroleum seeps. These seeps are places where fossil fuels and petroleum products leak out of the Earth instead of being trapped deep below the ground. In these seeps, bitumen, asphalt, and tar bubble up into pools. Additionally, bitumen is the main fossil fuel component of oil sands. When bitumen combines with asphaltines a solid is formed that is useful for paving roads

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. Russian D6 is a type of residual fuel, mainly used in power plants and larger ships.

D2 is a refinery abbreviation for Gasoil. It is the second distillate from the crude, and can be used without reformers and additives. So, the first engines used D2 as fuel – before petrol cars as we know them today was invented. That is because the engine invented by a German called Diesel, requires no spark plugs.

Jet fuel is a mixture of a variety of hydrocarbons. Because the exact composition of jet fuel varies widely based on petroleum source, it is impossible to define jet fuel as a ratio of specific hydrocarbons. Jet fuel is therefore defined as a performance specification rather than a chemical compound. Furthermore, the range of molecular mass between hydrocarbons (or different carbon numbers) is defined by the requirements for the product, such as the freezing point or smoke point. Kerosene-type jet fuels (including Jet A and Jet A-1, JP-5, and JP-8) have the majority of their carbon number distribution between 8 and 16 (carbon atoms per molecule), while more-refined, more-expensive wide-cut or naphtha-type jet fuels (including Jet B and JP-4) have most of their a carbon chains 10 to 14 atoms long for enhanced performance in polar regions