A panel of independent experts working under the National Research Council report that modern, light-duty diesel engines, which meet clean-air standards, are a viable means of improving fuel economy.

Clean diesel offers a potential reduced fuel consumption of 30 to 40 percent over gasoline engines, making the once filthy fuel a method of propulsion worthy of inclusion on the rostrum of available technologies.

The findings of the panel are in response to a request by the National Traffic Safety Administration for an update to a study conducted in 2001 on fuel efficient technologies. At the time, neither diesels or hybrids were included in the results.

In 2001, diesel engine could not measure up to standards for clean air and hybrids were, at best, a niche technology. Improvements in diesel engines and the increasingly ubiquitous presence of hybrids on American roads made it clear a review of fuel efficient technologies was in order.

The new study, however, does not deal to any large degree with fuel cell or all-electric vehicles. In the group's interim report the committee said it, "does not expect commercialization of fuel cell vehicles or widespread marketing of all-electric vehicles before 2020."

The group's final report will be published mid-year. The NHTSA will compile its initial set of standards to comply with the nation's new energy law by April 1, 2009 to be effective for the model year 2011.