<P> A flexible - fuel vehicle (FFV) or dual - fuel vehicle (colloquially called a flex - fuel vehicle) is an alternative fuel vehicle with an internal combustion engine designed to run on more than one fuel, usually gasoline blended with either ethanol or methanol fuel, and both fuels are stored in the same common tank . Modern flex - fuel engines are capable of burning any proportion of the resulting blend in the combustion chamber as fuel injection and spark timing are adjusted automatically according to the actual blend detected by a fuel composition sensor . Flex - fuel vehicles are distinguished from bi-fuel vehicles, where two fuels are stored in separate tanks and the engine runs on one fuel at a time, for example, compressed natural gas (CNG), liquefied petroleum gas (LPG), or hydrogen . </P> <P> The most common commercially available FFV in the world market is the ethanol flexible - fuel vehicle, with about 50 million + automobiles, motorcycles and light duty trucks manufactured and sold worldwide by mid 2015, and concentrated in four markets, Brazil (29.0 million by 2017 - YTD), the United States (17.4 million by the end of 2014), Canada (1.6 million by 2014), and Europe, led by Sweden (243,100). In addition to flex - fuel vehicles running with ethanol, in Europe and the US, mainly in California, there have been successful test programs with methanol flex - fuel vehicles, known as M85 flex - fuel vehicles . There have been also successful tests using P - series fuels with E85 flex fuel vehicles, but as of June 2008, this fuel is not yet available to the general public . These successful tests with P - series fuels were conducted on Ford Taurus and Dodge Caravan flexible - fuel vehicles . </P>

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