There are plenty of ways to improve your gas mileage.
1) Avoid high speeds. Driving 65 mph instead of 75 mph can cut your fuel costs by 15%.
2) Use the grade of motor oil recommended by your car’s manufacturers. Using a different motor oil can lower your gasoline mileage by 1 to 2 percent.
3) Improve your mileage by 3.3% by keeping your tires properly inflated.
4) Increase your fuel economy by 5% by placing items in your car or trunk instead of on a roof rack. Roof racks can cause drag.
5) Buying a hybrid can greatly increase your miles per gallon. Depending on your driving style and what you are currently driving, you could possibly get twice the amount of miles per gallon than your current vehicle.
For more ways to save at the pump, Daily Fuel Economy has a blog dedicated towards increasing your gas mileage. You may want to check it out.