View Here : What Is Flex Fuel
Some flexible fuel vehicles have labels on the door, indicating that they can use E85 fuel. Look for a badge on your vehicle’s body. Many flexible fuel vehicles have badges indicating it is a “FlexFuel” or “FFV” vehicle.
Re: Flex fuel Sep 07 2012, 1:23am No its not bad, it just means that the truck will run on E85 ethanol, its cheaper fuel where its avaliable but also gets worse gas mileage.