Increase your fuel economy

Modifying your driving habits can save you money and increase your fuel economy by up to 47 percent.That 100-pound (45-kilogram) suitcase in your trunk will decrease your fuel economy by 2 percent; eliminating weight from your ride can greatly improve your gas mileage.
Since well-inflated tires have less contact with the road, they encounter less friction. Therefore, the engine doesn't have to work as hard to move the car. -If you want to get even more efficient, you can switch from regular tires to low rolling resistance tires. Low rolling resistance tires are harder than regular tires, so they encounter even less friction. Treehugger.com reports that using low rolling resistance tires can lead to a 6 percent increase in fuel economy [source: Treehugger.com]. There are some downsides to the tires, however. They're a lot harder than regular tires, so your car's ride and handling may suffer. Also, don't run out and buy low rolling resistance tires unless you were planning on replacing your tires anyway. The savings in fuel won't offset the cost of new tires. Wait until you need new tires before getting them. Finally, work with your mechanic or tire shop to find the proper low rolling resistance tires for your car.