Studies about fuel economy are all around, but with the coming of the hybrid and electric cars, other possibilities exist. You have for example regenerative braking. With a normal car, all the energy from the car is converted to heat when you brake. With regenerative braking, at least a part of that energy can be converted to useful energy (electricity). If you use a hybrid or electric car, that electricity can then be used again to power your car. According to HowStuffWorks, we can reduce our energy use with up to 45%. This means that less electricity has to be produced as well, since we use less. With the danger of our fuel running out soon (around 100 years), this regenerative braking becomes more and more important. Every bit of energy that we can save is positive.
I believe that we have to reduce our fuel consumption as much as possible, and this is a good way of doing so, but maybe there are more interesting, more promising options?