For too many years, misguided diesel enthusiasts have gotten away with “felony air pollution.” And it ain’t cool.

For the most part, hot rodders are just as concerned about the environment and air quality as the general population, and I’d argue that because their mechanical IQ is higher, they are perhaps more aware, and in some cases, more concerned. We all tend to dig things like increased efficiency, light weight, and the over-arching concept of having your proverbial performance cake, and eating it too.

There are, nevertheless, some not-so-enlightened hobbyists who have decided to maximized their carbon footprint just for the fun of it. Most egregious is the fact that this is done without any particular performance gain. These folks own big, honking diesel trucks—almost always brand new—that often top the three-ton mark. They can belch black clouds of smoke at will, for the sole purpose of showing off. 

While searching for info on this new trend, I dug up this photo, with a corresponding blog from a diesel speed shop website that (incredibly) had this to say: “There’s a common misconception about black smoke being emitted from diesel-powered vehicles. Most people seem to think that because there is black smoke, it is ‘dirty.’ In fact, diesel burns MUCH cleaner than gasoline.” And while it is true that state-of-the-art diesels are much cleaner when tuned properly, this is not the case when black smoke is belching, and certainly not for the truck in the accompanying photo.

You’ll remember that we did a story on Mike Racke’s twin-turbo diesel-powered Chevelle in our June issue. Mike’s making over 1,000 hp, and when he’s got the accelerator pedal on the floor, there’s not so much as a wisp of black smoke. Why? Because Mike has tuned his fuel delivery so that there is a minimal amount of excess fuel remaining in the exhaust. He’s extracting the maximum amount of energy, and wasting nothing.

Some diesel tuners out there like to tune for extreme excess diesel (fuel enrichment). It’s a bandage approach that disguises the fact that they just don’t have the tuning chops, and that that their owners are too cheap to upgrade to a bigger turbo (the biggest limiting factor in making more power in a diesel). Irrespective of this, I’ve noticed that a few diesel owners just “get off” on making big clouds of black smoke, and it’s my guess that these guys are asking shops for this kind of tune.

Besides being wasteful and just plain rude, this black, sooty smoke is, in fact harmful, and is highly regulated by the EPA for a variety of reasons. Black diesel soot is essentially incompletely burned fuel that is chock full of parafins, ash particulates, sulfates, silicates, and long-chain hydrocarbons, which are precursors to acid rain. I’m not going to get into all the health risks, but it’s fair to say the guy who wrote the comment above has inhaled too much of the stuff.