According to the makers of ScanGauge you can save up 30% by using a gas mileage monitoring gauge to test your gas mileage. This sort of goes hand in hand with slowing down but it also reinforces how well you are doing.
In my personal experience, I have gone from getting an average of 30 mpg to an average of 39. I drive about 20k miles a year so if gas stays at 3.25/gal I will save $500.00 in a year. That’s enough money to help feed several children in Nicaragua through Hope of Joshua.