Gas Mileage Improvements: Can You Win 10 Million Dollars?
Although gas mileage devices have nearly doubled the actual mileage most cars get in the last 75 years, progress on this front has never been slower. Looking back over the last 20 years or so you will see very little improvement.
Source: automotive-journal.org

Police use gas-saving plan and rotate vehicles (The Allen American)
Though gas prices have risen in the last five years, the administration at the Allen Police Department has enacted a gas savings plan aimed at reducing the amount of fuel the department uses.
Source: www.allenamerican.com

Turning exhaust heat into mileage gains (The News Journal)
WARREN, Mich. — The stinky, steaming air that escapes from a car’s tailpipe could help us use less gas.
Source: www.delawareonline.com