E85 weighs 6.59 pounds or 2.99 kilograms per US gallon, making it slightly heavier than regular gasoline. Let us quickly sum up what E85 means. For example, the E stands for ethanol-based gasoline, and the 85 means there is at most 85% ethanol in the, For example gasoline mix. If your car does not indicate that it can take E85, please don't fill it up with E85. E85 is corrosive with most rubber and plastic materials and can clog up your fuel system with debris.