A new vehicle or car-pooling or biking to work may not be possible for everyone (self included). Here are some things that make a difference in existing vehicles.
Observe the Speed Limit
Over 50 percent of the energy required to move a vehicle down the road is spent overcoming aerodynamic drag (pushing air out of the way). When driving faster, the aerodynamic drag and rolling resistance increase. Consequently, the fuel economy decreases rapidly at speeds above 60 mph.
Overdrive Gears and Cruise Control
When using overdrive gears it's possible to still drive at highway speeds, but the engine speed decreases. Overdrive gears reduce both fuel consumption and engine wear. Also, using cruise control on highway trips helps maintain a constant, steady speed rather than a variable speed and as a result helps reduce fuel consumption.
Anticipate Traffic Situations
Anticipating traffic conditions ahead and not tailgating can improve gas mileage by 5 to 10 percent. This driving strategy is not only safer, but it will also reduce wear on tires and brakes. When driving in the city, nearly 50 percent of the energy needed to power a vehicle is for acceleration. Unnecessary braking wastes that energy. Also, accelerating quickly causes the engine to enter a less efficient "fuel enrichment mode."
Avoid Unnecessary Idling
Most vehicles do not need to be warmed up. In fact, no matter how efficient the car is, unnecessary idling wastes fuel, costs money and pollutes the air. If waiting for more then couple minutes in a drive-up lane, turn off the engine. Also, do not leave the car idling while running into a store for a "quick" errand. This is especially hard on a car during in the hot summer months and is an open invitation for auto theft.
Tire Maintenance
Be sure the tires are properly inflated. If the label lists a psi range, use the higher number in order to maximize fuel efficiency. Radial tires can be under inflated yet still look normal, so check the tires with a gauge. On average, tires lose about one psi per month and one psi for every 10-degree drop in temperature. Under inflated tires cause fuel consumption to increase by as much as six percent, cause the tires to wear quicker and can make it difficult to handle the vehicle. Be sure wheels are aligned and brakes are properly adjusted to minimize rolling resistance.
Change Your Motor Oil and Air Filter Regularly
Some oils contain additives that reduce friction and may increase a vehicle's fuel economy by three percent or more. Look for the Energy Conserving API label. This symbol indicates that the oil is certified, fuel-efficient oil by the American Petroleum Institute (API).
The car's air filter keeps impurities in the air from damaging internal engine components. Not only will replacing a dirty air filter improve fuel economy, it will protect the engine. Clogged filters can cause up to a 10 percent increase in fuel consumption.
Take a look at the
VortecCyclone add-on for some vehicle air filters. This small item has been stated to increase efficiency up to 30%.
Keep Your Engine Tuned-up
Studies have shown that, depending on a car's condition; a poorly tuned engine can increase fuel consumption by as much as 10-20 percent. Following the recommended maintenance schedule in the owner's manual will save fuel, help the car run better and last longer. There are now even more efficient spark-plugs on the market that claim to increase your vehicles fuel efficiency.
Pick up a discount card
A lot of gas stations have a specific credit card or 'discount' card. Pick one up and use it to save everytime you fill up. It may only seem like pennies, but it will add up.
http://www.fueleconomy.gov/feg/driveHabits.shtml