As your speed increases, your aerodynamic drag increases in an exponential fashion. Driving 62 mph (100 km/h) vs 75 mph (120 km/h) will reduce fuel consumption by about 15%.

By anticipating the traffic and applying slow steady acceleration and braking, fuel economy may increase by as much as 20%.

Keep tire air pressure at the level recommended by your vehicle manufacturer. A single tire under inflated by 2 PSI, increases fuel consumption by 1%.

Increased friction decreases gas mileage. Using the wrong grade of oil or not changing it frequently enough increases friction. Check your manual for recommended grades and change intervals.

When the air conditioner is on it puts extra load on the engine forcing more fuel to be used (by about 20%). The defrost position on most vehicles also uses the air conditioner.

Windows open, especially at highway speeds, increase drag and result in decreased fuel economy of up to 10%.

Remove excess weight from the car. Your trunk or van is not a storage area on wheels. Unless you plan on needing it this trip take it out of your trunk. Naturally emergency equipment is the exception. An extra 200 pounds will cost you one mile per gallon. That's about a 4% reduction in mileage.

Remove roof racks and other unnecessary items attached to the exterior of the vehicle. When not being used, these items can increase wind drag and result in decreased fuel economy.

Proper maintenance avoids poor fuel economy related to dirty air filters, old spark plugs or low fluid levels.

Maintaining a constant speed over long distances often saves gas.

Remove the sand bags from your trunk in the spring and pack lightly for long trips.

If you anticipate being stopped for more than 1 minute, shut off the car. Restarting the car uses less fuel than letting it idle for this time.

When buying a new vehicle examine the vehicle's rated fuel efficiency. Usually choosing a small vehicle with a manual transmission will provide you with great fuel economy.