That's what they call the technology behind new ultra-low sulfur diesel fuel that is coming down the pipe this summer and will be widely available at the pump by October. The new mix has only 3 percent of the stinky, smoky sulfur now found in diesel fuel.

If it lives up to the name, clean diesel will help clear the air we breathe. It will give American drivers the chance to buy fuel-efficient diesel cars and trucks that are popular in Europe and Asia but unavailable here.

Environmental regulators say the new fuel will cut tailpipe pollution in old vehicles by 10 percent to 30 percent. But the real impact will come when a new generation of diesel cars, trucks and buses hits the road.

Starting in 2007, diesel vehicles will be equipped with emission-control devices that could not be installed in older cars because they work only with ultra-low sulfur fuel. The same thing happened with gasoline cars two decades ago, when getting rid of lead made it possible to install catalytic converters.

Scientists say the new clean diesel fleet will reduce unhealthy exhaust by a whopping 90 percent.

"We consider this a very significant improvement in terms of emissions from diesel engines," said Tom Mather, a spokesman for the state Division of Air Quality. "The big benefits will come down the road as the old vehicles are retired and the new vehicles have this technology. But we'll still see some benefits in the old engines, too."

Can this really be true? Lots of us remember the noisy, soot-belching trucks and buses -- and a few diesel cars -- that blackened the air as recently as the 1980s. Diesel vehicles are cleaner these days, but they're still more of a pollution problem than gas engines.

The clean diesel transformation will be phased in over a few years, covering trucks and buses and later extending to diesel-powered trains, ships and other nonhighway engines.

The old rule allowed 500 parts per million of sulfur for highway fuel, with even more sulfur permitted for off-road use. After June 1, the Environmental Protection Agency says, 80 percent of all diesel fuel refined or imported in the United States must have sulfur levels no higher than 15 parts per million. That goes up to 100 percent in 2010.

Diesel pumps must have green labels to make it clear which sulfur mix the customer is getting. The old 500 ppm mix is labeled "low sulfur" and illegal for use in new cars, trucks and buses starting in 2007.

The nonprofit Clean Diesel Fuel Alliance, an industry and consumer group, says drivers of older diesel vehicles need not worry about which fuel they use. No changes in fuel economy or performance are expected.

Will any of us want to buy new diesel cars?

Only a few Volkswagen models, a Jeep, a Mercedes Benz and several pickup trucks are available as diesels in the United States now. More are expected on the market over the next few years.

Three VW turbo-diesel models rival the best gas cars for fuel economy, but their tailpipe problems disqualify them for federal tax credits of up to $3,000 that reward buyers of the Toyota Prius and other gas hybrids.

Auto industry analysts have predicted that clean diesel models will break that barrier. Honda says it will produce a diesel car as clean as the cleanest gas models.

Check the Clean Diesel Fuel Alliance (www.clean-diesel.org) or the Diesel Technology Forum (www.dieselforum.org) for more information about the new technology.

Teen drivers

How can you help make your teen a safe driver? Find out about some promising options online and in a new book at The N&O blog, Crosstown Traffic (http://blogs.newsobserver.com/crosstown/). And share your own ideas.