OK, so this is silly, but my mind is free to think about such things when I'm trying to get an extra mpg here or there, right?
I was following a slow convoy of cars up a hill, and wondered how awesome it would be if I could just hitch myself the the car in front and let him do all the work of lugging the weight of my car. Of course, this would have to happen imperceptibly... oh, I know: tractor beam!
So I wondered what futuristic technologies would you like to implement on your cars to get the edge in the attaining better mileage?
(Yes, I know teleportation would save the world, and warp reatrors don't even need gasoline. This is about single things to improve real world gas mileage.)