I have heard many times, and read again recently, that your driving habits (e.g., how fast you accelerate, whether you stick to the speed limit) will affect your gas mileage.
I have also read in many reviews of hybrid cars that one of the really neat features of such cars is a dashboard indicator that tells you your current gas mileage in real-time, so you can adjust your driving habits to maximize your mpg's.
My question is, why don't all cars have such indicators? Why can't every vehicle tell you how many miles per gallon you're getting right now?
(Link via Lifehacker.)