[MetroMPG]

It's a commonly repeated myth that aerodynamics only "come into play" at highway speeds. (You often see people mentioning 60 mph in this myth.)

If you plug your vehicle stats into our aero calculator tool (in the tools section of the garage... link at the top of the page under the header image) you'll see that even at just ~40 mph, about half your fuel is being burned to overcome aero drag.

So while slowing down will definitely help most, ignoring easy aero mods is leaving money on the table.