Argonne mechanical engineer Steve Ciatti tackles some of the most persistent myths surrounding the technology. “We all have this image of trucks spewing black, dirty smoke,” Ciatti said. This smoke consists of particles from diesel exhaust: soot and small amounts of other chemicals produced by the engine. And when it comes to diesel engines, there is an obscene amount of myths that many peers ignore because of the rumors they have heard about these masterpieces. The first and most common myth is that diesel is very dirty. But that's why it's a myth, because diesel is actually cleaner than gasoline.