10% MPG improvement
I've discovered a technique to get over 10% improvement in fuel economy. Simply put it involves varying your speed on hills. If done in a consistant and precise manner your savings can be quite dramatic. My Prius went from 43 MPG to 50.
It helps to have a cruise control that will click your speed up or down 1 MPH at a time and it helps a lot if you have a graph like the Prius does that shows current MPG readings.
This technique should not be done in heavy traffic since it involves varying your speed between 5 to 20 MPH.
You use the the down hills to gradually click up your speed until you reach your maximum speed at the bottom and then on the up hills click down the speed until you reach your minimun speed at the top of the next hill. If you have the Prius, use the graph and click up the speed when the bar graph shows 75 MPG and click down the speed on the up hills when it drops to 25 MPG.
After a while you learn to anticipate and even do it withpout looking at the graph (which is actually kind of dangerous in that you are not watching the road as much as you should).
The Prius graph shows the average MPG per fill up and gives instant results and instant gratification.