School of hard NOx

For light-duty diesels to succeed in the U.S., they'll first have to pass ultra-stringent 2007-2010 emissions standards-and keep costs reasonable. Aftertreatment technologies are critical for diesels to make the grade.

When announced five years ago, the current Tier 2 U.S. federal emissions standards looked like a death sentence for light-duty diesel engines in the U.S. market. For the first time, all cars and light trucks are required to meet the same tailpipe emissions levels, regardless of fuel type.

Gasoline engines are expected to breeze through Tier 2 certification with only minor calibration tweaks. “I don't see any real challenges,” noted John German, Honda of America's Manager of Environmental and Energy Analysis.