Frankly, standardization is often the only option given the limits of a universal technology standard. 1  1. Standardization lag: It takes time to understand a problem domain well enough to make a proper standard.
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.
There are several ways to tell if your car is a flex-fuel vehicle: Check the gas cap. Beginning in 2006, FFV manufacturers started putting distinctive yellow gas caps on their vehicles. Check the fuel door. FFVs often have a sticker inside the fuel door that tells you which fuels can be used.