"Clean" next-generation diesel cars are storming into the fuel economy race, rivaling hybrid vehicles especially in the luxury car segment.

The word "diesel" may conjure up the image of large, rumbling trucks spewing out thick, black smoke. But the planned release of high-tech diesels by various carmakers is about to wipe out that negative image.

"The days of noisy, stinking diesels are now over," said motor industry analyst Aritsune Tokudaiji, author of more than 40 books on automobiles.