flexiblefuel

Flexiblefuel, or flexible-fuel vehicles (FFVs), are motor vehicles designed to run on gasoline blends containing ethanol or on pure ethanol. They are capable of operating on a range of mixtures from any amount of ethanol up to 100% ethanol (E100) depending on the market and vehicle specification.

FFVs carry sensors that determine the ethanol content of the fuel at fill-up, using a fuel composition sensor, and the engine control unit (ECU) adjusts the air-fuel ratio, ignition timing, and other parameters to optimize combustion for the chosen blend. The fuel system uses ethanol-compatible materials to resist corrosion and swelling.

In the United States and Canada, many automakers offer FFV models that can use gasoline or fuels up to E85. In Brazil and some other markets, ethanol is widely used, and flexible-fuel vehicles are designed to run on blends from 0% to 100% ethanol. Ethanol availability and blend levels depend on infrastructure and policy.

Advantages include reduced dependence on petroleum, potential emissions benefits with certain feedstocks, and fuel-price flexibility. Limitations include lower energy content of ethanol, which reduces fuel economy on high-ethanol blends; higher octane can permit higher compression; ethanol can pose compatibility challenges for older vehicles and infrastructure; regional availability of ethanol blends and cold-weather performance may vary.

Flexible-fuel technology emerged in the late 20th century, with mass-produced FFVs appearing in North America in the 1990s, and widespread adoption in Brazil as part of the sugarcane ethanol program.