Though we cover diesels from other makers--BMW, for instance--most of our coverage of new diesels here on GreenCarReports has to do with Volkswagen. That's because they simply sell more diesels in the States than any other maker.

But even Volkswagen has had some hiccups, having to stop sales for several months until they could meet more stringent emissions regulations with a new generation of "clean diesel" vehicles.  Those TDI models (Jetta and Touareg, and soon, the 2010 Volkswagen Golf TDI as well) have a strong following.

VW diesels also seem to return higher mileage than the EPA's fuel-economy numbers would indicate. So much so, in fact, that VW hired an independent testing firm to check out the Jetta TDI's real-world mileage. Their results--38 mpg city / 44 mpg highway--were 24 percent and 10 percent higher than the EPA figures of 29 mpg city / 40 mpg highway.

From that groundwork has emerged a new website, TDI Truth & Dare, or as VW calls it, an "unedited consumer blog forum." It's devoted to "truths" about VW's clean diesel technology and "dares" to show exactly how well it works.

"First, visitors will learn the truth about clean diesel technology by understanding the facts," says Volkswagen. "Second, the forum will dare visitors to get involved in the alternative fuel discussion by participating in online events like the "Tank Wars" fuel efficient driving challenge and using applications like "Diesel Finder" and "Savings Calculator." Additionally, the blog will post relevant facts and discussions from Volkswagen as well as third party sources and consumers to keep visitors up to date on the latest diesel conversation ... in a voice that is unique to Volkswagen."

With the Volkswagen logo all over the site, you may not be surprised that clean diesel comes off pretty well. We specially liked some of the videos, including the Golf TDI covered in ice at -25 degrees F to show that diesels will start right up even at very low temperatures.

But despite big plans laid a couple of years ago, many European carmakers are now nervous about whether Americans will take to clean diesel in an era of $2/gallon gasoline. Not to mention a downturn in which many people simply aren't buying cars at all, and those who are may be downsizing or economizing.

We like diesels, especially for long-distance cruising (like the Euro-spec Audi A6 TDI we tested recently). For stop-and-go urban driving, hybrids are better suited--and will displace more fuel--since they can switch off their engines and run short distances on electric power.

But while Mini and Audi may still launch small diesels in the US, we'd put our money on Volkswagen as the one manufacturer who can continue to sell diesels in volume and profit from it.