A flexible fuel vehicle is one that can operate on:
(1) alternative fuels (such as M85 or E85)
(2) 100 percent petroleum-based fuels
(3) any mixture of an alternative fuel (or fuels) and a petroleum-based
fuel.
Flexible fuel vehicles have a single fuel system to handle alternative
and petroleum-based fuels.
(Courtesy of Energy Information Administration, U.S. Department of Energy)