By dirty I meant smog and cancer causing emissions, not CO2. And, regarding concerns of global warming,
".. Laws that favor the use of diesel, rather than gasoline, engines in cars may actually encourage global warming, according to a new study. Although diesel cars obtain 25 to 35 percent better mileage and emit less carbon dioxide than similar gasoline cars, they can emit 25 to 400 times more mass of particulate black carbon and associated organic matter ("soot") per kilometer [mile]. The warming due to soot may more than offset the cooling due to reduced carbon dioxide emissions over several decades, according to Mark Z. Jacobson, associate professor of civil and environmental engineering at Stanford University..."
Of course, old diesels are especially bad in this regard.
Dunno about those L engines. I had the impression they were all duds, but that may be wrong.