Fix formula and add average fuel consumption to trips model (#327)

* Fix formula and add average fuel consumption to trips model

mytoyota/models/trips.py

@@ -129,18 +129,39 @@ def ev_distance(self) -> Optional[float]:
 
     @property
     def fuel_consumed(self) -> float:
-        """The amount of fuel consumed.
+        """The total amount of fuel consumed.
 
         Returns
         -------
-            float: The fuel consumed in liters if metric or gallons
+            float: The total amount of fuel consumed in liters if metric or gallons
 
         """
         if self._trip.summary.fuel_consumption:
             return (
-                round(self._trip.summary.fuel_consumption / 4546.0, 3)
+                round(self._trip.summary.fuel_consumption / 1000.0, 3)
                 if self._metric
-                else (self._trip.summary.fuel_consumption / 1000.0)
+                else round(self._trip.summary.fuel_consumption / 3785.0, 3)
+            )
+
+        return 0.0
+
+    @property
+    def average_fuel_consumed(self) -> float:
+        """The average amount of fuel consumed.
+
+        Returns
+        -------
+            float: The average amount of fuel consumed in l/100km if metric or mpg
+
+        """
+        if self._trip.summary.fuel_consumption:
+            avg_fuel_consumed = (
+                self._trip.summary.fuel_consumption / self._trip.summary.length
+            ) * 100
+            return (
+                round(avg_fuel_consumed, 3)
+                if self._metric
+                else round(235.215 * avg_fuel_consumed, 3)
             )
 
         return 0.0