Flex fuel E85 refers to a type of automotive fuel containing 85 percent ethanol and 15 percent regular gasoline. Ethanol 85 functions much the same way as regular gasoline, powering cars and trucks classified as flexible fuel vehicles, or FFVs. However, it forms from different substances than pure gasoline, making it suitable for use only in cars listed as flexible fuel, which have special engines and fuel systems built to handle it.
The number 85 following the "ethanol" indicates the percentage of ethanol, a corn-based alcohol, that this gasoline contains. Although formed almost entirely of ethanol, this alternative fuel requires some amount of gasoline to ensure cars operate smoothly. This is particularly true in the cold winter months, when car engines need gasoline to turn over.
In addition to operating on ethanol fuel blends, FFVs may use regular gasoline without sustaining damage. This dual-fuel capacity provides reassurance to vacationing or commuting FFV drivers in areas where flex-fuel stations do not exist.
Many drivers select FFVs for perceived environmental benefits. Ethanol derives from non-finite sources and is a domestic fuel, which reduces reliance on foreign oil suppliers. Despite the reduction in oil dependency, however, ethanol fuel is generally less fuel-efficient than regular gasoline and costs more, making FFVs no more cost-effective than cars using traditional gasoline.