Greener Cars and Trucks

Dirty Diesels?

Diesels generally don't make the green grade, says the ACEEE. That's because, even though they consume less fuel than their gasoline counterparts and therefore release fewer greenhouse gas emissions per mile driven, diesels spew far more particulates and other nasties from their tailpipes than conventional gas engines. Nitrogen oxides, sulfur oxides and hydrocarbons, all pollutants that cause urban smog, contribute to global warning and negatively impact human health.

But don't discount diesels just yet: they're trying to clean up their act. Today's diesels pollute much less than those of yesteryear. And as prices at the pump continue to climb and savvy shoppers demand more fuel-efficient (and cleaner) vehicles, manufactures are responding with advanced emission control technologies that will allow diesels to meet forthcoming EPA emissions standards.

Some enterprising individuals, reluctant to relinquish their old, classic diesel workhorses (diesels are well-known for their long-lived engines), are turning to biodiesel to tidy up their tailpipes. Derived from vegetable oils and animal fats, biodiesel is a cleaner, greener fuel that significantly reduces end emissions, especially sulfur oxides and hydrocarbons.

Using biodiesel fuel requires few or no engine modifications; some drivers even report smoother running cars and, sometimes, a little hike in fuel economy. The primary obstacles to increased biodiesel use are its higher cost (B20, a blend of 20 percent biodiesel and 80 percent petro-diesel, costs 13 to 22 cents more per gallon than standard diesel fuel), and limited availability and production capacity. Only a handful of public biodiesel stations operate in the United States, although the number is steadily growing.