Utah television personalities known as the Diesel Brothers have asked a federal court to dismiss a lawsuit against them that says the group violated the Clean Air Act.

Cole Cannon, the group's legal counsel, said the Diesel Brothers believe the case against them is "overly broad" and ought to be at least reduced in scope.

Local environmental group Utah Physicians for a Healthy Environment filed suit earlier this year, alleging that the four men made illegal modifications to the pollution-control systems on diesel vehicles at their Utah businesses. The Diesel Brothers, as they are known, appear in a reality TV show by the same name that airs on the Discovery Channel.

Cannon said the Diesel Brothers — named in the suit as David "Heavy D" Sparks, David "Diesel Dave" Kiley, Joshua "Redbeard" Stuart and Keaton "The Muscle" Hoskins — believe that Utah Physicians means well, but that it was misled by misinformation online. It is possible to "roll coal" in a diesel vehicle without modifying the emissions systems, he said, so the online videos collected by the environmental group as evidence for its legal complaint do not necessarily prove that the Diesel Brothers modified the trucks' emissions systems.

"There's no video of anyone removing a catalytic converter from a vehicle," he said.

Furthermore, he said, not all of the trucks depicted belonged to the Diesel Brothers. The motion to dismiss also requests that the individuals and their businesses be removed from the lawsuit.

Cannon said that the Diesel Brothers invited Utah Physicians to tour their shop before the lawsuit was filed in an attempt to clear up the misconceptions, but that the group declined.

Representatives of Utah Physicians did not respond to a request for comment. Reed Zars, an attorney representing Utah Physicians, has said that negotiations between the two parties "never really went anywhere."

In a brief responding to the motion to dismiss the case, Utah Physicians held that its case was neither too vague nor ambiguous, but that it was built on "more than one hundred very detailed factual allegations … derived directly from the Defendants' own statements and promotional materials."

Cannon declined to comment on which specific modifications may have been made to the Diesel Brothers' trucks. But the Diesel Brothers deny that the vehicles were modified as alleged by Utah Physicians, he said.

But he said his clients sincerely hope for a speedy resolution of the suit that would be "mutually beneficial to the truck community and to the environment."

Cannon said ambiguities in the Clean Air Act have left many car enthusiasts wondering whether the law applies to race cars and competitive off-road vehicles. He said he hoped the Utah Physicians case would lend some clarity to the issue.

A hearing on the motion to dismiss the case has been scheduled for June 27.

epenrod@sltrib.com

Twitter: @EmaPen