JP-4 is a colorless to strawcolored liquid with the odor of gasoline and/or kerosene. JP-7 is a liquid, usually colorless and with the odor of kerosene. JP-4 can be made by refining either crude petroleum oil or shale oil. It is called a wide cut fuel because it is produced from a broad distillation temperature range and contains a wide array of carbon chain lengths, from 4- to 16. It consists of approximately 13% (v/v) aromatic hydrocarbons, 1.0% olefins, and 86% saturated hydrocarbons.1 JP- 7 is made by refining kerosene, a product of refined crude petroleum. It was developed for use in advanced supersonic jets because of its thermal stability and high flash point.Aviation fuels consist primarily of hydrocarbons (paraffins and cycloparaffins or naphthenes primarily but also aromatics and olefins). Paraffins have a high hydrogen-tocarbon ratio, with a high heat release per unit of weight and a cleaner burn than other hydrocarbons. Cycloparaffins have a lower hydrogen- to-carbon ratio and produce less heat release but increase the density and reduce the freezing point of the fuel. Aromatic hydrocarbons are a good energy source but produce smoke on burning; therefore, the maximum levels are restricted (20–25% by volume in JP- 4, 5% by volume in JP-7). Olefins are similar to paraffins but are unsaturated (double and triple C-C bonds) with lower hydrogen-tocarbon ratios, are the most reactive of the hydrocarbons, and are allowed at only 5% by volume in JP-4. Benzene is present as a contaminant at less than 0.5% in JP-4. Other ingredients of lesser importance are sulfur and sulfur compounds as well as additives to improve performance (antioxidants, metal deactivators, fuel system icing inhibitors, corrosion inhibitors, static dissipater additives).