Cálculo Flex is an Android app developed by Allan Siriani, designed to help car owners make informed decisions about whether to fill up with gasoline or ethanol. The app is free to download and falls under the Utilities & Tools category.

The app's standout feature is its simplicity. All you need to do is enter the price of gasoline or ethanol, and the app will show you how much ethanol should cost to make it a better deal than gasoline, based on a 70% ethanol to 30% gasoline ratio. This makes it easy for users to determine which fuel is more economical at any given moment, saving them time and money in the long run.