Removing unnecessary items from your vehicle saves fuel. It takes energy to move the extra weight around. An extra 100 pounds in your vehicle can reduce your miles per gallon by up to 2 percent.
The Department of Energy estimates that 1.2 billion gallons of fuel were wasted in 2005 as a result of driving on underinflated tires. Tires can deflate naturally, by as much as 1.5 PSI (pounds per square inch) a month. Experts estimate that 25 percent of automobiles are running on tires with lower than recommended pressure. Fuel efficiency is reduced by 1 percent for every 3 PSI that tires are under-inflated. So, keeping your tires properly inflated translates into a free tank of gas a year and reduces CO2 emissions too. You can also consider purchasing fuel-efficient tires.
According to the U.S. EPA, you can improve your fuel economy by 1-2 percent by using the manufacturer's recommended grade of motor oil. Use an energy-conserving grade of motor oil. For information of how to do this correctly and environmentally visit http://www.epa.gov/epawaste/.
According to the U.S. Department of Energy, replacing a clogged air filter can increase your mileage by 10 percent.
As much as 30 gallons of gasoline could be lost annually to evaporation when the fuel cap is not fully tightened. Loose, damaged or missing gas caps cause 147 million gallons of gas to evaporate each year, according to the Car Care Council.
Fill gas tank during cooler evening hours to cut down on evaporation. Avoid spilling gas and don't "top off" the tank.
Wind resistance can reduce mileage, so you can maximize your mileage by removing luggage racks, roof-top carriers, and ski racks when they are not needed. Experts at Edmunds.com say that even keeping your car washed and waxed improves aerodynamics.
(Tips compiled from NCDAQ, ecodrivingusa.com, fueleconomy.gov, mass.gov.)