Adjusting the miles per gallon of your vehicle is simple! When editing or creating a trip, you can easily adjust your MPG within the Trip Itinerary.
With a trip loaded on the map, tap the Trip Itinerary.
Once the Trip itinerary is open, tap the Trip Menu to open more trip details.
Once open, begin adjusting your MPG and choose your gas type! You can also edit the name of your trip, and add a description.
(Currently you can only adjust your MPG via iOS)