See also: Automating LEAP with the API, Fuels
The LEAPFuel class represents a Variable for a single Fuel whereas LEAPFuels is a collection of all Fuels in the area. The Fuels collection is a property of the LEAPApplication class.
Please use the Script Editor for documentation of the properties and methods of the Fuels API. The right-hand pane of the Script editor fully enumerates all collections and objects in the LEAP API.