What Happened To The Diesel Brothers? The Controversy Behind The Emissions Lawsuit

There's no shortage of reality TV series that focus on skilled mechanics modifying cars, trucks, and SUVs in sometimes outlandish fashion. But fans of Discovery's "Diesel Brothers" would be quick to argue that few of those series are quite as unabashedly entertaining. They might even say the diesel-powered beasts seen on the show are some of the most impressive to grace the airwaves.

If you've never watched the show, "Diesel Brothers" follows David "Heavy D" Sparks and David "Diesel Dave" Kiley as they modify diesel-powered vehicles at their Sparks Motors garage in Salt Lake City. In doing so, they often invest tens of thousands of dollars in each vehicle, fashioning them with all manner of upgrades, including even massive monster-truck-style engines. The transformations can be fascinating to watch, with the series' stars and their gearhead buddies displaying a vast well of knowledge in the course of every project.

Of course, working with diesel power plants presents its own set of issues, in particular when it comes to navigating the tricky waters of emissions regulations. Indeed, even the series' ace cast and crew found themselves ensnared in a controversy a few years back when Utah Physicians for a Healthy Environment filed legal papers accusing the Sparks Motors team of some dodgy emissions practices, including the ill-advised "deleting" of diesel power plants in their shop. Here's how that lawsuit shook out.

The Utah physicians' group filed a federal lawsuit in 2016, alleging that Sparks Motors had undertaken the sale or modification of multiple vehicles that violated emissions restrictions set forth by the Clean Air Act. The physicians' group said it had acquired a vehicle the Sparks Motors team had outfitted with a straight pipe modification that allowed it to "roll coal" – which is illegal under local laws in six states, including Utah, and involves the purposeful release of thick black exhaust while accelerating. 

During the legal proceedings, the physicians' group's attorneys presented evidence showing that the vehicle their clients purchased was releasing 36 times more pollutants than if its emissions controls were working, due to those controls being disabled. So it wasn't a surprise that when the ruling was handed down in 2020, the TV stars were found to be in violation of the law, and ordered to pay fines in the amount of $851,451.

They were also informed that if found tampering with diesel-powered vehicles' emissions controls again, they'd be held in contempt of court, making further penalties likely. The Sparks crew appealed the decision, but in 2021, the ruling was upheld by a federal judge in Salt Lake City. Nonetheless, the Discovery stars persisted in their attempts to limit the damage, and in January 2024, eventually did have some luck in court, winning a $225,000 reduction of the financial penalties levied against them.  

Team Sparks has wisely kept clean since that initial court ruling. But fans have noticed that new "Diesel Brothers" episodes are no longer airing on Discovery, leaving some to wonder if the series was canceled, although the Sparks crew took to YouTube to debunk the cancellation rumors in 2021. The release of Season 8 episodes in 2022 backed up the claims that Discovery had not canceled the series. Even so, the lack of a ninth season renewed questions about the status of "Diesel Brothers."

While Discovery has not officially announced the end of the show, in a 2023 statement on the Sparks Motor Company website, the reality stars confirmed that "Diesel Brothers" was indeed over – but said they'd taken it upon themselves to stop the show. They said they wanted to return to their roots via self-produced YouTube videos that would give them more control over what they're doing and when they're doing it. Given the time and content constraints that no doubt come with the production of a network-backed TV series, one can hardly blame Team Sparks for opting to go it alone.