Purchasing a car is likely the second largest investment you will make – and one that you will likely have to live with for at least the next few years – so you want to make the best, cleanest, most fuel efficient, safest, and cost effective decision. For my husband and I this decision has lead us beyond the land of hybrid vehicles and into the land of diesel engines.

The 2009 Green Car of the Year award went to a Turbo Diesel Injected (TDI) vehicle – the Volkswagen Jetta Clean Diesel (TDI). This is the first time the award has gone to a clean diesel vehicle. For Americans, a diesel car probably sounds like an old, dirty engine, but its time for all of us to get back on the diesel bandwagon. Europeans have been driving these new diesels for years, but these cars have only recently been able to meet the stringent American emissions standards. In fact while adventuring to Copenhagen, Denmark, it was hard not to see one of these (or the wagon version) cars on the street — even as taxi cabs!

Hands down, this is a performance vehicle. Its powerful, even though it is only a four cylinder vehicle. Because my husband and I have been seeking a car that would allow us to become a one car family and yet still have plenty of space for lugging things home, someday growing a family, and hopefully space for a dog, we looked at the sportwagon version of the VW TDI. Testing driving this car, we were nearly sold, but it was the little bonuses for the price that really sealed the deal. This car has gadgets galore — and most of them are standard! Between the Bluetooth (which even allows you to play music over the speakers that is streamed from your iPhone), the touch screen radio, and the digital dashboard readouts, this car has just about everything a geek could want! Further, the seats fold down perfectly flat, the front seats (and back!) are heated, and the side view mirrors have a defrosting option. All around, this car is fun to drive.

Its not all fun and games in these cars though. Some of the toys genuinely help the driver drive more efficiently. Much like the Ford and the Toyota hybrids which display the fuel efficiency of the car, the VW and Audi clean diesel cars show the average fuel economy for your current driving trip and your tank of fuel. They also show you instant fuel economy based on the speed you are traveling. These gauges help drivers learn which driving styles generate the best fuel efficiency for the vehicle. Of course, also like most of the hybrids, most clean diesel cars also offer built in navigation which can also help you increase your fuel economy by showing you the most efficient way to get from place to place.

But what’s so great about the clean diesel technology and how is it different today than it was years ago? First of all, today’s diesel engines are highly efficient. The VW Jetta Sportswagon, for example, gets 30mpg in the city and 41mpg on the highway. Best yet, these mpg stats are likely to be surpassed. (It is a Jetta TDI that currently holds the world record for best fuel efficiency with 67.1mpg.) With 236 foot pounds of torque, this vehicle is powerful to say the least, able to move quickly from a standing start and pass other moving cars with a light tap of the petal. In comparison, old diesel engines were known for being loud, hard to start, and belching smoke, a far cry from these clean engines, even if they were efficient for its time. With prices for diesel fuel not much more than that of gasoline and the prices staying far more steady, its no wonder why Americans are beginning to again look towards these new technologies.

Interestingly, the Audi A3 clean diesel TDI is the 2010 Green Car of they year. This makes two years running for a clean diesel cars to win the coveted award.

So if you are wondering what it is my husband and I purchased… you guessed right! The VW Jetta Sportswagon TDI. We call her “Gretta the Jetta.”

The time has finally come when my husband and I will be consolidating to just one car and I can hardly wait! While car shopping is certainly not my favorite pastime, the prospect of getting to vote with my wallet for the cars that should be on the road is exhilarating.

Considering that in the United States, the largest group among American’s owning at least one car, actually own three, it’s no small feat to go from two cars to one. We live close to a metro train stop and usually take public transportation to work. We rarely are using two cars at the same time, these days, so it make this transition to stepping down to one car that much easier.

We currently lease a small, but efficient 2007 Honda Civic and own a small, but as efficient as she can be 2001 Toyota Rav4. The Rav4 is my baby, surviving the worst car crash I have ever been in, experiencing Vermont winters (she’s only a 2×4), and seeing me through my tumultuous 20s. While she may not have been the most fuel efficient cars of her time, she has been a dear friend. Replacing her towing capacity, reliance, and comfort while maintaining top notch fuel efficiency is our number goal in finding the perfect vehicle – the question is: are there any new automobiles on the market up to the challenge?

The simple answer right now is: we just aren’t sure yet. We have looked at the obvious choices like all the hybrid models currently available to the U.S. market. We have researched the conventional engine models which have “good” gas mileage, and we have begun the investigation into new diesel technologies which are not only cleaner than your father’s diesel engines but more efficient too. But there are other aspects to consider too – do they have the room we need? Are they something I want to be in for a long ride half way across the country when we visit the family? Will they last and have excellent resale value five to eight years from now? And sadly, will the manufacturer even exist by year’s end let alone for the life of the vehicle?

We are both professional environmentalists, who both even advocate for strong climate legislation for a living, so it is important to us to make the right decision in a time when consumers can really make a statement just by their purchase.

Over the next few days and weeks, I will be chronicling our efforts to find the perfect auto and hopefully making it easier for you to follow suit when you are ready to look for your next four wheel best friend. Have a question or have advice, comment below!

Do you complain about traffic? Do you have a long commute? Did you know that cars account for 20% of the U.S. global warming emissions? 20%! You should continue to drive, but have you stopped to consider what the alternatives might be?

Walk – Do you ever drive to places that you could just as easily walk to? Helps the waistline too!

Bicycle- Wouldn’t you just love to whiz past that long line of cars as they wait in rush hour traffic? This is multi-tasking people! Exercise reduces stress! And with the rising cost of gasoline, who couldn’t use a few extra bucks?

Mass transit- Metro/Subway/Bus.  Whatever your community offers! Sometimes this may not be the most convenient way to go, but have you considered how much easier it would be to let someone else do the driving, while you sit back and read? At least check it out! The schedules and low prices might astound you!

Fuel efficient car – not everyone can own a hybrid (but if you can…do…they rock!). If you are in the market for new wheels, however, at least look for a car that gets good mileage! No words to the Hummer drivers here…we would like to give everyone a chance…