Road Block: You just filled your tank. Now it’s empty. How can you conserve gas?

Best Route: Changing the way you drive can raise your fuel economy by as much as 50 percent, says mechanical engineer Ron Graves, the director of the Fuels, Engines and Emissions Center at the Oak Ridge National Laboratory, in Knoxville, Tennessee. Here’s how to increase fuel economy.

Take it easy. Aggressive driving — like jackrabbit acceleration when lights turn green and hard braking at reds — burns a lot of gas. Just smoothing out your starts and stops can save you up to 30 percent in gas mileage.

Watch your speed. “Most passenger cars get their best fuel economy between 45 and 55 miles per hour,” Graves says. And each five miles per hour that you drive above 60 miles per hour costs you the equivalent of about 15 cents a gallon (based on a price of $2.25 a gallon.

Keep the engine tuned, the air filter clean, and the tires filled to the proper pressure.

Reduce air conditioning use — unless you’re on the highway, where the drag of open windows sometimes consumes more power than running the A/C.

For more fuel-savings tips, visit the U.S. Department of Energy website at www.fueleconomy.gov.