Hydrocarbons

Like other petroleum products, gasoline is comprised of hydrocarbons that are obtained from crude petroleum. Crude petroleum oils are composed of four major hydrocarbons, i.e. paraffinic (also known as alkanes), olefins (alkenes), naphthenic (also known as cycloalkanes) and aromatic hydrocarbons.

Aromatics are good octane enhancers. However, heavy aromatics may cause engine deposits, particularly in combustion chambers. These deposits increase tailpipe emissions of hydrocarbons and nitric oxide/nitrogen dioxide (NOx). Moreover, their combustion leads to the formation of carcinogenic benzene. Therefore, lowering the aromatics level in gasoline will reduce benzene and toluene emissions, but it may increase aldehyde emissions. The aromatic content of gasoline is directly proportio