AUTOS
A greener way to ride
Many people already know that keeping their car maintained (tires inflated, filters clean) is a good way to improve mileage. And good mileage is what having a green car is all about: The less gas you use, the less pollution you'll emit. Here are other ways to "green" your wheels.

Rely on your cruise control.
Good for the environment: "Where you use the most gas is during acceleration," says Jen Boulden, co-founder of eco-lifestyle site IdealBite.com. "The most fuel-efficient way to drive is to minimize your acceleration, which is what cruise control does."
Good for you: "You'll get up to 15% better mileage," she says. And you won't need to worry about getting a speeding ticket (when you set your cruise control at or below the speed limit, of course).

On hot days, keep your windows up -- and the air conditioner on -- when you're driving on the highway.
Good for the environment: It might be counterintuitive, but you use less fuel with your windows up and the air conditioning on than you do with the windows down and the air turned off. "The air conditioner doesn't draw more fuel -- and certainly not more than the drag you would get with your windows open," says Thomas Kostigen, co-author of "The Green Book."
Good for you: With your windows up, you can actually hear the radio as you cruise along the freeway.

Try not to let the car idle.
Good for the environment: Red lights and stop signs aside, idling is a waste of gas. When you run in to, say, the post office -- even for 30 seconds -- turn off the car. "When you're stopped and idling, you're getting zero miles per gallon," Kostigen says. "And there's no science behind the misconception that it takes more fuel to start the car again."
Good for you: Fewer fill-ups means money in your wallet.

Choose re-refined motor oil.
Good for the environment: Re-refined oil is recycled. It already has been used, but it's processed again to remove water and impurities. Why is it better? Because it takes less energy to produce than virgin oil.
Good for you: Tests show that re-refined is just as good as (and might even be better than) virgin. And the price is usually about the same, if not better.

Buy a partial zero-emission vehicle (PZEV).
Good for the environment: A PZEV is about 90% cleaner than the average new car in terms of emissions; some are so clean that what comes out of the tailpipe is actually cleaner than the air in smoggy urban areas. And it's an option on many familiar makes and models. "A lot of people have these vehicles and don't know it," Kostigen says. "You can see it on the sticker of the car, and it's also in the owner's manual."
Good for you: PZEVs have a 15-year/150,000-mile warranty (better than most). And sometimes these cars cost as little as $100 more than a non-PZEV model.

Use a commercial carwash.
Good for the environment: "Commercial carwashes use about 100 gallons less water per wash" than washing your car yourself, Kostigen says. "[Some] reuse the water, so it's recycled back into the system. They filter out the soap and chemicals."
Good for you: One less chore to do on sunny Saturdays.

Join a car share.

Good for the environment: Car shares, such as Zipcar and Flexcar, let urban dwellers who don't always need a car have quick, easy and inexpensive access to one. Membership gives you the right to use a fleet of cars parked around town (any of which you can unlock with an electronic card that you keep). You pay a small fee with each use and return the car to the spot where you found it. Eco- and community-friendly, this system cuts down on gas usage, pollution and traffic congestion because car sharers are more likely to drive only when necessary.
Good for you: No car insurance, gas or maintenance to worry about (or pay for); those costs are included in the fees. And unlike traditional car rentals, car shares can be used by the hour. Plus, most car-share rentals can be reserved online or over the phone 24/7.