Well Blue Rotor Ronin,
download the manual and you will see, that the little garmin helpers have all in, you need
From calculating sunrise and sunset at any given point, route planning (50 routes to be saved - you can fly them backwards as well), fuelplanning and so on, just select the fuelrate you burn and the winds.
Bye the way, my old GPS90 can do that as well.
Grretings Flying Bull