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gasohol, a gasoline extender made from a mixture of gasoline (90%) and ethanol (10%; often obtained by fermenting agricultural crops or crop wastes) or gasoline (97%) and methanol, or wood alcohol (3%). Gasohol has higher octane, or antiknock, properties than gasoline and burns more slowly, coolly, and completely, resulting in reduced emissions of some pollutants, but it also vaporizes more readily, potentially aggravating ozone pollution in warm weather. Ethanol-based gasohol in which the ethanol is made from corn is expensive and energy intensive to produce, and can damage rubber seals and diaphragms and certain finishes if the ethanol is present in higher concentrations. Since 1998, however, many American automobiles have been equipped to enable them to run on E85, a mixture of 85% ethanol and 15% gasoline. Methanol-based gasohol is also expensive to produce and is toxic and corrosive, and its emissions produce cancer-causing formaldehyde. See also automobile.

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Gasohol is a term used for the mixture of 10% ethyl alcohol (also called ethanol or grain alcohol) with gasoline . Ethanol raises the octane rating of lead-free automobile fuel and significantly decreases the carbon monoxide released from tailpipes. It has also been promoted as a means of reducing corn surpluses. By 2001, 2.2 billion gal (8.3 billion l) were being produced a year and this number is expected to rise to 4.6 billion gal (17.4 billion l). However, ethanol also raises the vapor pressure of gasoline, and it has been reported to increase the release of "evaporative" volatile hydrocarbons from the fuel system and oxides of nitrogen from the exhaust. These substances are components of urban smog , and thus the role of ethanol in reducing pollution is controversial.

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gasohol A mixture of petrol (gasoline) and alcohol (i.e. typically ethanol at 10%, or methanol at 3%), used as an alternative fuel for cars and other vehicles in many countries. The ethanol is obtained as a biofuel by fermentation of agricultural crops or crop residues, for example sugar cane waste. Many cars can also use a mixture of 85% ethanol and 15% petrol, called E85. Ethanol-based gasohol has a higher octane rating and burns more completely than conventional petrol, thus lowering some emissions. However, the ethanol can damage certain engine components, such as rubber seals. Methanol-based gasohol is more toxic and corrosive, and its emissions include formaldehyde, a known carcinogen.