Diesel fuel is a mixture of hydrocarbons obtained by distillation of crude oil.
The important properties which are used to characterize diesel fuel include cetane number (or cetane index), fuel volatility, density, viscosity, cold behavior, and sulfur content.
Diesel fuel specifications differ for various fuel grades and in different countries.
Diesel—whose first engine concept was designed to use coal dust as the fuel—recognized that liquid petroleum products might be better fuels than coal.

Diesel fuel is a mixture of hydrocarbons—with boiling points in the range of 150 to 380°C—which are obtained from petroleum. Petroleum crude oils are composed of hydrocarbons of three major classes: (1) paraffinic, (2) naphthenic (or cycloparaffinic), and (3) aromatic hydrocarbons. Unsaturated hydrocarbons (olefins) rarely occur in the crude. It should be noted that the terms ‘paraffinic’ and ‘naphthenic’ seem to be obsolescent; we use them because they are still common in the petrochemical industry. In modern chemistry, the respective groups of hydrocarbons are called alkanes and cycloalkanes.
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