[PaleMelanesian]

It partly depends on your normal driving routes. If you do lots of highway driving, sure, aerodynamics would be a big improvement. If, like me, most of your time is spent at city speeds (below 45 mph), the big costs to mileage are in accelerating and braking and idling. A gauge is useful to know how to manage those optimally. On the highway, aerodynamic drag is the biggest cost and there's not much accelerating and braking and idling.