Things that affect the environmental impact a car makes:

Gas mileage – This is where it all starts. More miles for less gas means reduced dependence on fossil fuels, lower emissions and a greener future.

The surprise was that in some situations, like highway driving, an internal combustion engine with adaptive technology like the Ford EcoBoost, will actually get you better mileage (not to mention way more power) than a hybrid. For a city driver like me, a hybrid is great. But since my husband commutes on the highway every day, we might be able to get even better mileage with a traditional car. That was a humbling moment!

Weight of the car – This is also tied in with safety. If you can make a car lighter, then it takes less horsepower to move it, and you can make the engine smaller, which makes it even lighter. That also means you can get better gas mileage (see above).

Of course, if you make a car out of a lightweight material like aluminum, then you want to add safety features, which could add weight back on. Innovation in new materials that are light, durable and safe helps make a car more fuel efficient. But you don't want those materials to be made of crazy, toxic, petroleum-product plastic components, either!

Composition of the components – Next time you're in your car, think about what will happen to all of the parts when you're done with it. Besides recycling the metal and plastic components, the seat cushions, the fabric coverings and carpets can all be broken down or reused. In fact, 95% of the vehicle can be recycled!

Even better is to use materials with a lower environmental impact in the first place. At Ford I learned about some really cool research they're doing to create components from renewable resources, like bamboo fabrics and soy foam.

Yes, foam, as in the material seats are made. Usually this material is made from oil, but Ford developed a process using locally-grown soy. I drove a Mustang with these seats and had no idea they were any different from any other seat, although they were quite comfortable. So even though the Mustang has a rather gas intensive (and let admit it, very fun) V8 engine, it still gets some eco-friendly points for the renewable resources used in construction.

Granted, you're not going to convince George Clooney to trade in his Smart Car for a Mustang merely based on the soy foam seats or a faux suede interior made from recycled soda bottles. However, if gearheads are going to buy their muscle cars regardless of CO2 levels, every little bit is going to help.

Building practices – A big part of the carbon footprint equation is how much energy it takes and how much waste it makes to create something. Back in 2004 Ford transformed the historic Rogue Rouge (even though Rogue is funnier, just a typo!) factory in Michigan into a state-of-the-art green facility. Interestingly enough, it's the site of the factory where Henry Ford first built the Model A ... out of iron.

The Rogue plant boasts the world's second largest living roof, a rainwater treatment system designed to clean 20 billion gallons of rainwater annually, and water heated by solar powered collectors.

That means a burly F150 pick up truck built at the Rouge factory could actually have a better carbon footprint than a compact car built in a foreign factory where there are lax environmental regulations.

Scalability of the solution – Hybrids are a great innovation, but from a global perspective there aren't that many of them, which limits the aggregate benefit of driving one. On the other hand, the internal combustion engine EcoBoost technology, which gives a 20 percent fuel efficiency boost to millions of cars, will have a far greater positive environmental impact. New ultra-low-sulfur diesel fuel burns more efficiently and cleanly than gas vehicles, including those hybrids. This makes a big difference in Europe, where more than half of the cars sold are diesel.

The mix will change over time, as more factories are built to produce hybrids and other vehicles that leverage new, cleaner, technology. Bu for now, the biggest benefits are coming from surprising corners.

Interactive features that make you a better driver – Admit it, we've all been trained by video games to learn from flashing lights on animated screens. The display on my Prius gives me real time information about the engine, including whether we're on electric or gas power. Honda Insight's Eco Assist is a dashboard feature that gives you feedback to be a more efficient driver, giving you visual cues to do things like slow down or brake more gently.

The Ford Fusion system takes it one step further in the video game direction. In addition to all of the usual systems feedback, as you drive you grow a tree, earning more leaves for efficient driving. You also lose leaves for inefficient driving. I imagine this creates some interesting competitions in certain households.

Decisions, Decisions
Many factors go into the decision to buy a car, from all of these environmental considerations, to price, to emotional connection a brand. Having grown up driving Fords, and because they actively reach out to the blogger community with information and opportunities to learn from their senior staff, I'm a pretty big fan.

That said, the auto industry is in a time of active development, and almost all of the companies are coming out with innovations, from plug in hybrids to battery electric vehicles (BEVs) to the sexy and sporty (and Prius blind spot sized) Tesla I almost backed into the other day.

The important thing is to take the time to educate yourself about all of the aspects of your car buying choices, going beyond gas mileage. Ask about the sustainability practices of the manufacturer, request post-consumer content carpets. Reward the companies, like Ford, that care enough to dedicate resources to find solutions that keep our environment in balance while getting us to work, school, and out on the occasional road trip.