There's a middle ground: Avoiding unnecessary acceleration & deceleration.

I don't hyper mile, but I do get far better gas consumption than rated. I let people merge, leave safe follow distances, and don't aggressively close traffic gaps which actually improves traffic flow by reducing waves of jams.

http://www.smartmotorist.com/traffic-and-safety-guideline/tr...

Mind you, I've been in cities where this type of behavior may get you murdered, but where I live this creates a more relaxing drive. If I feel like speeding I'll go to a race track :)