Diesel fuel is a mixture of liquid hydrocarbons. It is got by distilling and refining petroleum, usually at a temperature of 150-370 °C. Diesel fuel is used as diesel engine fuel. The quality of diesel is defined by ČSN EN 590. The quality of diesel is indicated by the cetane number, which expresses its combustion quality during compression ignition. The cetane number therefore has a parallel with the octane number of spark-ignition engine petrol. The higher the cetane number of combustion-ignition fuel is, the better quality the fuel has. In this case, a direct injection engine better starts, has better performance, and its running is quieter and smoother. Exhaust gases then contain a lower amount of undesirable combustion products. Better performance decreases fuel consumption. Diesel fuels with different low-temperature properties, depending on the season, are distributed on the Czech market as well as in most of the other EU countries. To modify these properties in order to achieve the desired level, a variety of additives is widely used. And to ensure the trouble-free operation of compression-ignition engines when there are severe frosts, so-called arctic diesel fuel with a filterability of less than -32 °C and a cloud point of less than -22 °C is produced.
Division of diesel fuel by suitability depending on climatic conditions and its distribution:
Summer diesel fuel – i.e. diesel fuel for temperate climate class B, from 15 April to 30 September, with a filterability of less than 0 °C
Diesel fuel for the transitional period – i.e. diesel fuel for temperate climate class D, from 1 March to 14 April and from 1 October to 15 November, with a filterability of less than -10 °C
Winter diesel fuel – i.e. diesel fuel for temperate climate class F, from 16 November to 28 February, with a filterability of less than -20 °C