E85 gas, also known as flex fuel, is a high-level combination of ethanol and gasoline that consists of 51 percent to 83 percent ethanol blended with gasoline. The percentage of ethanol depends on the region and season. E85 is not the same as regular gasoline, but it does contain gasoline. E85 should only be put in certain vehicles called flex fuel vehicles (FFVs), which have a fuel delivery system and engine that are designed to use it. Many drivers already own an FFV and do not even know it. To check if a car is an FFV, see the U.S. Department of Energy’s (DOE) fuel economy site or simply look for a few signs such as a yellow-colored gas cap, yellow ring around capless fuel fillers, or a flex fuel label on the fuel door. E85 generates more torque and horsepower than gasoline, burns cleaner, and leaves no residue. However, E85 gets less mileage than regular gas, leading to fewer miles per gallon. The pros of using E85 include less dependence on foreign oil, fewer air pollutants released into the atmosphere, and higher resistance to engine knocking. The cons of using E85 include being limited to use in flex-fuel vehicles, less energy per gallon, leading to fewer miles per gallon, and not being readily available in some regions. It is also important to note that ethanol is 25% less efficient than gasoline, so using E85 can lead to a decrease in efficiency by 21%.