Tire Pressure

• Periodically check your tires to make sure they are inflated to the manufacturer-recommended pressure. Even if your tires look fine, a lower-than-recommended pressure will negatively affect your gas mileage. If you do not already have one, buy a portable pressure gauge to keep in your glove compartment. Inflate the tires at a gas station or with a personal tire pump whenever they stray more than a few PSI below the recommended pressure.
  
  

Driving Technique

• For city driving, gradually increase your speed as you accelerate from stop signs or stop lights. Conversely, ease off the gas and slow down gradually, rather than holding down the gas pedal and then hitting the brakes heavily. On highways, do not drive faster than the speed limit. Popular Mechanics columnist Benjamin Jones claims to have increased his gas mileage from 30 miles per gallon to nearly 70 miles per gallon using efficient driving techniques, collectively known as "hypermiling."
  
  

Window Usage

• Use windows judiciously. Air conditioning requires a compressor and fans to circulate cold air through the car's interior, both of which must draw their energy from the gasoline supply. Slate magazine says that depending on the ambient temperature and your air conditioner's efficiency, air conditioning can eat up anywhere from 3 to 20 percent of your gasoline. However, the drag produced on the car at high speeds is also likely to increase gas consumption by 10 to 20 percent. A good rule of thumb is to use natural ventilation for city driving, but air conditioning for highways or thoroughfares.
  
  

Oil Changes

• Change the oil less than shops recommend. A clean supply of oil is essential for a car to function, but energy is involved in the production of petroleum-based and synthetic oils, not to mention environmental drawbacks inherent in their disposal. Although car shops may recommend changing oil every 3,000 miles, owner's manuals often recommend changes every 5,000 to 7,500 miles. According to Earthtalk magazine, some synthetic oils are designed to last up to 25,000 miles, or one year before changing. Ask your mechanic about synthetic oil options and bring the car in for oil changes according to your own schedule.