These refining processes take the less and more volatile hydrocarbons found in petroleum, and turn them into hydrocarbons that have not only the correct volatility, but also other desirable characteristics necessary for good engine performance. These characteristics are discussed later. Finished gasoline, then, is a blend of hydrocarbons having a similar volatility range, made from distillation and refining processes. There are over 200 individual hydrocarbons, as well as trace concentrations of other compounds, naturally present in petroleum. To these are added specialty chemicals that add to or enhance the performance of the hydrocarbons.  

Composition and properties of gasoline are determined by the crude oil from which it was derived, what refining processes were used to produce the gasoline, and the nature of the additives used to add to or enhance the gasoline's performance.  

By characterizing certain physical, chemical and combustion properties of gasoline, we can predict (in part) how it will perform in internal combustion engines. These properties are summarized in the American Society for Testing and Materials Standard Specification for Automotive Spark-Ignition Engine Fuel (ASTM Designation D 4814). ASTM is a technical organization that develops a consensus of voluntary performance standards for materials and products. This Standard Specification applies to almost all gasoline sold in the United States. Other gasoline properties not specified in ASTM D 4814, which are also important to performance, are summarized in Table 3 at the end of this handbook.  

TABLE 1:  

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