Enlarge / A thoughtful soul decides to poison the air as he drives through the infield at Daytona International Raceway during the 2016 Rolex 24 race. (credit: Jonathan Gitlin)

I remember the first time someone rolled coal on me. It was 2006, and I was driving to work at the University of Kentucky. It was a bright, sunny day in Lexington, and I had the roof down and was stopped in traffic behind a large pickup truck with decidedly non-standard exhaust pipes exiting straight up behind the cab. Whoever was driving the pickup evidently noticed the Miata in his mirror and enveloped me in a thick cloud of soot when the lights changed.

As automotive subcultures go, intentionally modifying your truck's diesel engine to make extra pollution is one of the more antisocial ones out there. According to the US Environmental Protection Agency, diesel trucks with disabled emissions controls are far more widespread than you might think and emit more pollution than the diesel engines that got Volkswagen such hefty fines.

In 2016, Volkswagen agreed to a pair of court settlements totaling nearly $16 billion after it was caught selling diesel vehicles fitted emissions defeat devices. In total, the VW scandal affected more than half a million cars and SUVs sold in the US, which produced up to 40 times the legal limit of nitrogen oxides (NO _x ) when in daily operation.

Enlarge / A 1980s Mercedes-Benz diesel belches exhaust fumes in London. People expected diesel engines of this vintage to be dirty, but we had a right to expect that diesel engines sold over the past decade complied with emissions laws. Turns out, they don't. (credit: Richard Oliver/Getty Images)

In 2020 it seems more usual to read about the US Environmental Protection Agency rolling back pollution laws or arguing that big business should be allowed to do what it wants . But apparently the agency does occasionally work as intended. Earlier this week, together with the US Department of Justice and the California Air Resources Board, it held Daimler AG—parent company to Mercedes-Benz—accountable for selling diesel vehicles fitted with emissions defeat devices.

EPA and CARB found that all was not right with the Daimler's diesel engines in the wake of the 2015 Volkswagen emissions scandal . EPA told Daimler it was going to conduct some additional tests of the company's four- and six-cylinder diesel engines "using driving cycles and conditions that may reasonably be expected to be encountered in normal operation and use, for the purposes of investigating a potential defeat device."

In doing so, it discovered several auxiliary emission control devices that were not described in the homologation paperwork submitted by Daimler. In total, about 160,000 Sprinter vans and about 90,000 Mercedes-Benz vehicles are affected, between model years 2009 and 2016.