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.”

As I mentioned some time ago, my husband and I have been in the market for a new vehicle – but not any old car! As professional advocates on climate change issues, it is extremely important to us to make a choice that supports our daily efforts to improve fuel efficiency, keep our air clean, and reduce our carbon footprint.

When we’ve spoken about out interest in purchasing a new car with our friends, they all seem to simply think the obvious choice for us is a hybrid vehicle. But just because the vehicle includes hybrid technology, does not always mean that it’s the most fuel efficient. New technologies are always coming out and while we rely on manufacturers to tell consumers about the benefits, most have done a pretty lousy job. The educated car buyer is challenged to keep up with the innovations, learning the benefits, which manufacturer is using the technologies and when they will be brought to the marketplace. It’s not an easy task.

All hybrid technology is not created equal – and they differ from one manufacturer to another.Learn more about hybrids by checking out a post I wrote about them some time ago. You cannot rely upon car salesmen to tell you about the technology as many have not taken the time to learn about it or will be able to explain it well. Do your own research.

Compare vehicles that include hybrid technology with conventional models making sure to look at price, miles per gallon, and even maintenance. If you are more of a long distance, highway driver, hybrid vehicles may not increase your mpg enough to make it worth the extra money. For you, it may make more sense to seek out a conventional or diesel (TDI – Turbocharged Direct Injected) vehicle with excellent highway ratings. More on TDI another day… For those of you who are more short distance, city traffic drivers, hybrids may better suit your needs since the vehicle recharges the battery while breaking and operates utilizing the battery while slowing and stopping.

It’s important to also realize that hybrids will soon be coming out with another big improvement – plugs! No, this doesn’t mean you will be required to plug in your car or park near an electricity source. What it means is that you will have the option to charge the battery of the car with electricity from your home, allowing the vehicle to rely on the battery more than the gas tank. Still you can always fill up at the local station and still recharge the battery through slowing and stopping. Best of all, this improvement to the hybrid technology will come with a battery with much improved energy saving capacity. Hopefully, theses cars are only right around the corner, so if you are not quite in the market for a new car but are just starting to think about it, look out for new plug-in hybrids coming to a car dealer near you in the next few years – if not sooner!

Still, while the U.S. market has just barely more than a handful of hybrids currently available, they simply do not seem to fit our bill when it comes to picking a car. Sure the Toyota Prius, the best selling hybrid currently on the market, is worth a look and remains on our list, it does not have the hauling capacity we had hoped to maintain. The capacity is ok, and certainly doable but for a young couple likely to one day use the car for cross country trips, kids, and our occasional furniture shopping, it is only barely as big as we want – even with the seats folding down flat (a major perk in our book!). We do not prefer the relative low quality and lack of comfort of the Ford Escape and while the Saturn Vue was a pretty good ride, we felt it had very few tech options we wanted for the price, not to mention that we learned just after test driving that GM would be closing the line at the end of this year.

If price were no matter, the Lexus RX450h would be on the top of our list. It’s gas mileage is excellent (though could always be better!) and truly is an exquisite design of luxury. Unfortunately, that luxury comes with a hefty price tag that happens to be out of our ideal range.

So the question remains, will we find a vehicle that is both fuel efficient and family friendly in size which fits into our (hardly meager) price range at under $35,000? Stay tuned!