Gasoline, Reformulated

Characteristics

Gasoline is a volatile substance. Volatility, the propensity of a chemical substance to evaporate under normal thermal and pressure conditions, is a function of vapor pressure. One typical way of evaluating how volatile a fuel can be is by its Reid vapor pressure (RVP), which describes the rapidity with which fuels evaporate. Larger (smaller) values indicate greater (lesser) volatility. Measured in pounds per square inch (psi), there is no single satisfactory value of RVP for gasoline, as a suitable value depends on temperature (and by extension, season of the year). For example, a reduced volatility may be desirable under hot conditions, as it decreases the potential for vapor lock to occur. On the other hand, increased volatility under cold conditions makes it easier to start an automobile. In the United States, RVP standards must be met during summer by conventional gasoline.

Although gasoline is derived from crude oil, it contains numerous additives. These include such substances as toluene (to boost octane) and benzene (as an antiknock agent). Both gasoline's fundamental constituents, as well as the extra additives, contribute to the soup of unwanted chemicals emitted into the surrounding air.

Reformulated gasoline is gasoline that has been modified to lessen the toxic emissions released to the surrounding atmosphere. These discharges include nonmethane hydrocarbons (NMHCs), carbon monoxide (CO), and nitrogen oxides. The latter are nitrogen monoxide, also known as nitric oxide (NO) and nitrogen dioxide (NO2); collectively, they are commonly referred to as NOx. Carbon monoxide is one of the most noxious by-products of fossil fuel combustion, and the dangers of breathing concentrated amounts of this gas in enclosed areas are commonly known. Nitrogen oxides result from nitrogen and oxygen reactions occurring during the combustion of fossil fuels such as gasoline.

[Page 610]A cleaner burning fuel also needs to be usable by standard automobile engines. Reformulated gasoline is safe enough to use without affecting engine performance. Many major automobile manufacturers, including General Motors, Ford, Mitsubishi, and Nissan, support and endorse the use of the oxygenated fuels (fuels that have oxygen added to burn cleaner), noting the environmental benefits. Other manufacturers, while not issuing outright endorsements, note that oxygenated fuels may be used, though typically stating a disclaimer that ethanol (the oxygenating compound in some fuels) content be no more than 10 percent by volume. Additionally, there is no danger of engine or fuel system damage if users of reformulated gasoline switch to conventional gasoline in locations where the altered fuel is unavailable; the converse is true as well.

...