Grist.com weighs in not the nuts and bolts of fuel efficiency and has some great facts and pointers.

Some highlights:

The venerable car group (edmonds.com) found that using cruise control improved gas mileage by 7 to 14 percent, except in mountainous terrain.

 

Where you set the cruise helps, too. Driving at 50-60 miles per hour keeps fuel consumption down, so if cruise helps you follow the speed limit, then it has an additional benefit (conscience does make cowards of us all).The government has estimated that each 5 mph over 60 costs you 26 cents per gallon.

It helps to get these facts and figures deeply drilled in the brain so that while driving one can hear a ca-ching, ca-ching with every vroom vroom, sudden acceleration, or sudden stop. I wonder if anyone has ever developed a gas gauge that shows dollars and cents spent in real time in addition to volume left in the tank. Hmmm...