A few weeks ago, my friend let me borrow his VW Touareg SUV for the weekend. While most guys drone on and on before they let you behind the wheel of their precious ride, my friend reiterated just one thing: Only fill 'er up with diesel. At first, I thought he was joking. Here I was in this sleek, upscale ride, getting comfy in my posh leather seat—wasn't diesel for industrial, smog-spewing 18-wheelers? Wouldn't I have to go to a special truck stop gas station to fill up? The answer was a definitive "no" to both. I decided to look into the fuel to see why companies like Volkswagen, Mercedes, Audi, and BMW are placing their bets on diesel.

It's been time-tested. The first passenger model was a 1936 Mercedes, so there's been decades of improvement to the technology.

It's the way of the future. J.D. Power and Associates predicts that the number of diesel vehicles purchased in the U.S. will double by 2012.

It's greener. Like the VW Touareg I drove, many run on low-sulfur "clean diesel," which means it's 98.5% cleaner than 1970s-era diesel cars. According to the EPA, if 33% of American drives switched to diesel, we'd reduce our need for oil imports by 1.5 million barrels every day, or about 10% of our imported oil.

It goes farther. In Europe, diesel cars rule the road, since they're known for getting far more miles per gallon than conventional gas, and also for having more durable engines.

It may be cheaper. Not only will you save money if you get more mpg, but Congress also offers $3,400 in tax incentives on diesel cars.

What Do You Think?