but I drive my Prius at 55 and I am getting 55-60 mpg (and when I drove the standard 65 or so a few months back, I was getting about 46 mpg, thus my mileage has increased about 20% which is just about the difference in air resistance at the two speeds.)

If everyone HAS TO go 55 mph, how am I supposed to show off my intellectual superiority, green cred and moral virtue! Ever since I slowed down, I feel so smug, puffed-up and holier-than-thou that my previous sense of self-doubt has been thoroughly trounced. When most people are driving 55 because they fear a speeding ticket, my recently-attained habit -- done for smart, honorable reasons -- will become invisible.