Want to help save the planet but don't have the budget to buy a new car (hybrid, electric or flex-fuel vehicle)? Don't worry. You can reduce your carbon footprint on the road, and your fuel usage, just by changing the way your drive and maintain your current vehicle.

Here are some tips for greener driving, courtesy of the EPA and Department of Energy (DOE).

Related: 10 Surprising Ways to Help the Planet

Avoid aggressive driving (speeding, accelerating like you're in the Indy 500, braking excessively). This kind of driving can reduce your gas mileage by 33 percent on the highway and 5 percent in town, according to the DOE.

Drive at the speed limit. Gas mileage drops precipitously after you pass 50 miles per hour, and you'll also be safer.

Ditch that heavy roof cargo box. This can drag down your fuel economy by 2 to 8 percent on city streets, 6 to 17 percent on highways and 10 to 25 percent on the Interstate (assuming you're traveling 65 to 75 miles an hour). A rear-mounted cargo box will cost you only about 1 percent in fuel efficiency. The bottom line: Take off the cargo box when you don't need it.

Clean out your trunk for more fuel savings. Carrying an extra 100 pounds could set you back 1 percent in terms of miles per gallon.

Don't idle. Make it a habit to turn off the car when you're parked in front of the store waiting for someone.

Use cruise control if you have it. This helps avoid the temptation to continually speed up and slow down, which can really cut into your fuel efficiency.

Keep your car and tires in good shape. Check your vehicle's owner's manual for the check-up schedule, make sure your tires are properly inflated and use the recommended blend of motor oil. When you’re ready for new tires, consider buying tires with an energy-saving feature known as “low rolling resistance.”

Walk, bike, carpool, telecommute and use public transportation whenever possible to avoid using your car. If you’re able to leave your car at home just two days a week, you can slash your greenhouse gas emissions by an average of two tons a year.

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Buying green

When you're ready to buy a new car, go with the cleanest, most fuel-efficient vehicle you can find. The EPA advises consumers to lool for a car or truck with low greenhouse gas emissions. Take a look at the EPA's Green Vehicle Guide for more information. An updated fuel economy and environment label on new vehicles, including electric cars and hybrids, also makes it easier to comparison shop.

A new car can also make it easier for you to use renewable fuel. If you buy a flex-fuel vehicle (FFV), it can take either gasoline or E85, a fuel blend containing 80 percent ethanol from plant sources and 15 percent gasoline. (Check out the DOE’s Alternative Fueling Station Locator to help you find E85 and biodiesel fuel stations in your area.) Be aware, though, that a typically gas-guzzling vehicle that is also a flex fuel vehicle will spew out just as much greenhouse gas as usual if you use only gasoline in it.

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Diana is an award-winning writer and editor with more than 20 years' experience in magazine, video, book and digital journalism, with a specialty in health coverage. She was a longtime writer and news editor at the Center for Investigative Reporting; has written for publications from the Washington Post to the Times of London syndicate; and has served as a senior and/or consulting editor at Time Inc. Health, Hippocrates, HealthDay News Service and Reporting on Health. She was also editor in chief of Consumer Health Interactive, a national health and medical web site, and has reported on finance for Blueshift Research and PBS Frontline. Before joining SafeBee, she was editor of Bioenergy Connection, a national magazine about bioenergy at UC Berkeley. Her favorite safety tip: Wear a bike helmet.