This app was initially for personal use but is now free to anyone. It retrieves the current CAD$/USD$ exchange rate but allows you to override it.
If you are used to the USD$/gallon method, it calculates the equivalent USD$ per gallon price from the CAD$ per liter price you input. This is to quickly compare Canadian fuel prices in a manner US travelers are used to.
If you are in Canada, you can convert in the other direction. Input the current USD$ per gallon price and it will convert it to CAD$ per liter for your comparison purposes.
When you initially start the app, it will retrieve the current exchange rate for USD$ and CAD$. If the exchange rate cannot be retrieved (possibly no internet), it will show 9.99 and you will need to input/override the exchange rate you need.
The app defaults to the CAD$/L to USD$/G conversion but you can change that direction by pressing the toggle button.
When you are ready to convert a value, input the starting point (CAD$/L or USD$/G) and press the Calculate button (you might have to do it twice). It will return the desired dollar-to-volume pricing that you requested.
I was a COBOL programmer by profession almost 40 years ago. I am trying some new programming now, so go easy on me!