Avoid excess weight . Heavier cars use more gasoline than similarly powered lighter cars. Check your car or truck and remove any unnecessary items. For every 100 pounds you remove, gas mileage increases from one percent to four percent, depending on the size of the car and the engine. Maintain proper tire pressure.
Underinflated tires increase rolling resistance which in turn decreases gas mielage.
Check pressures when tires are cold. Use multi-grade oil . The average car on the road today could increase its gas mileage by six percent with a minor tune-up. A neglected car could realize 20 percent or more improvement with the same tune-up. Get newer cars serviced according to the manufacturer's recommendations.