Diesel engines for passenger vehicles have been popular in Europe for a while, in part due to tax policies that encourage their use. At present diesels account for about half of passenger vehicles sold over there. In the U.S., however, the diesel share of the market registers in the low single digits.

One benefit of diesel engines is that they can deliver more miles per gallon. A downside is that diesel fuel tends to be dirtier, generating greater particulate emissions. This week, however, the EPA's new regulations requiring a dramatic reduction (97 percent) in the sulfur content of diesel fuel took effect. As the Washington Post reports today:

The change promises to significantly cut air pollution caused by diesel emissions. Regulators say high concentrations of sulfur in the old diesel fuel poison the engine systems that clean exhaust of harmful pollutants. The biggest concern is particulate matter, one of the byproducts of engine combustion, said Margo Oge, director of the EPA's office of transportation and air quality.

According to the story, automakers may respond by introducing more diesel models.

Detroit automakers have pledged to expand diesel offerings, particularly in pickup trucks. J.D. Power and Associates projects that the diesel share of light-vehicle sales is expected to increase to more than 10 percent by the middle of the next decade from 3.2 percent in 2005. Japanese automakers are also stepping up development of diesel technology.

It will be interesting to see how consumers respond, and gas prices may play a role. With gas prices having settled (at least for the moment), U.S. consumers may be less eager to give diesels another chance.