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What's the deal with coal-rolling?

A diesel pickup leaves a cloud of dark smoke in its trail, known as 'coal-rolling.'
Toa55/Getty Images/iStockphoto
A diesel pickup leaves a cloud of dark smoke in its trail, known as 'coal-rolling.'

Nick Mott Welcome to the Big Why, a series from Montana Public Radio where we find out what we can discover together. I'm your host, Nick Mott. This is a show about listener-powered reporting. We'll answer questions, large or small about anything under the Big Sky. By Montanans, for Montana, this is the Big Why.

Today, Montana Public Radio reporter Edward O'Brien joins us to talk about a topic that really grinds some people's gears. Welcome back, Ed.

Edward O'Brien It is lovely to be here. Thank you so much, Nick. And yeah, this question comes to us from Flathead Valley listener Margaret Satchell, who asks, "What's the deal with coal-rolling?"

Nick Mott Okay. So, coal-rolling sounds to me like pushing hunks of coal downhill or something. What is it?

Edward O'Brien Well, if you've ever seen or experienced firsthand, a pickup pull alongside or in front of you and then belch out a huge cloud of black or gray exhaust — well, you've just been coal-rolled.

There are zillions of coal-rolling videos on the internet, but here's a particularly popular one. So let me set the stage. Bunch of young guys are in a diesel truck hauling a boat. They slowly pull up on a young woman walking along the road and. Well, here, take a listen:

[Truck driver] "Excuse me, ma'am. Do you smoke?".

[Woman] Yes, I do.

[Truck driver] "Stand by."

Edward O'Brien So if you missed that, after she confirms that, yep, she smokes, the driver, then stomps on his accelerator, peels out, leaving her covered head to toe in sooty black exhaust.

I bring this to the table because the listener who submitted her question said she drives an electric car and she's been coal rolled and so have some of her friends on bicycles.

Nick Mott So this is actually intentional? It's not just the result of like a junky old engine?

Edward O'Brien No, very intentional. Coal-rollers frequently pride themselves on driving some very high-end trucks.

Nick Mott Then why are they so smoky?

Edward O'Brien Well, rolling-coal is the result of modifications made to newer diesel engines. There are lots of ways to get it done, including special switches, tuners or big old fuel injectors. Whatever the method, the goal is to dump more diesel into the engine than it can handle. So all that exhaust is the result of diesel fuel not getting fully burned.

Nick Mott That sounds like a bunch of work to get done. How much does it cost?

Edward O'Brien Yeah. These tweaks can run anywhere from a few hundred to a few thousand bucks.

Nick Mott Okay, so I get what coal-rolling is, but why do people do it?

Edward O'Brien Yeah, first, a little history. Coal-rolling has deep roots in truck pull contests.

Unidentified [Truck pull announcer talking as diesel engines rev.]

Edward O'Brien These pulls are popular competitions in the motorsports world where seriously souped up diesels compete to haul the heaviest payload. The signature rolled coal exhaust display is all part of the pageantry. It eventually filter down into road trucks and became a cultural, even a political statement.

Nick Mott Wait, how does politics figure into it?

Edward O'Brien Well, let's let JW Montoya explain it. He's a really popular social media influencer in the diesel truck world. His TikTok alone boasts almost 300,000 followers. Here's an excerpt from one of his YouTube videos explaining the cultural aspect of rolling coal. And it's been slightly edited for time.

[JW Montoya] "People who drive hybrids or Priuses, especially a few years ago before Tesla, they were in a category known as 'environmentally friendly.' People used to roll-coal on those vehicles just to intentionally upset them. They're associated with being in a specific political party. So it's done intentionally just to kind of piss them off.".

Nick Mott This reminds me of some of the culture war stuff we see playing out these days. Is anything like this happening in Montana?

Edward O'Brien Oh, you bet it is. And when a former state lawmaker caught wind of it a few years back, she sponsored a bill to punish coal rollers.

[Sen. Christine Kaufmann] "Members of the committee. For the record, I'm Senator Christine Kaufmann ..."

Edward O'Brien Kaufman served 16 years in the Montana Legislature. Back in 2015, she introduced a bill that would have essentially prohibited those diesel engine modifications we've talked about.

Christine Kaufmann I was driving a Prius at the time and I had never heard of rolling coal and it had not happened to me.

Edward O'Brien But it had happened several times to one of her Helena constituents who brought it to her attention. Back in 2015. Bryan Flynn told the Montana Legislature — the Senate Highways and Transportation Committee — that he and some colleagues were coal-rolled several times in Helena. Once, a driver rolled Flynn and a friend as they were bicycling west of Helena on Highway 12. He says newer model black truck covered them in diesel emissions.

[Bryan Flynn] "When the smoke cleared, I made a comment to my friend. We tried to laugh it off. But about 10 minutes later the same truck came back from behind, did it to us all over again. This was a little more intimidating, and I didn't try to make light of it that time."

Edward O'Brien At that point, Flynn says, they turned around to head back to town and got coal-rolled twice more on the trip home.

Nick Mott Wow. Couldn't they report it to the police?

Edward O'Brien Well, according to Flynn, the exhaust was too thick to make out the license plate. Christine Kaufmann says the more she learned about rolling coal back in 2015, the angrier she got.

Christine Kaufmann
Montana Legislature
Christine Kaufmann

Christine Kaufmann You know, it's really bad for your health to breathe soot from diesel vehicles, particularly. And then the environmental costs that are created when you put that much additional soot into the air, and it just seemed to be for no reason other than to be offensive toward people.

Nick Mott So what became of that bill of hers to ban those modifications to diesel engines?

Edward O'Brien You know, it's funny. Kaufmann says she was really happy with the hearing it received and it easily passed out of committee. But a lot of legislators who supported it then changed their votes when it hit the floor, so it didn't pass.

Nick Mott Kaufmann mentioned the pollution associated with rolling coal. Just how dirty is it?

Edward O'Brien Really dirty. According to the Environmental Protection Agency, a 2020 EPA report says the owners of over a half million trucks across the country have illegally tampered with their emissions control systems over the past decade. The agency says that's equivalent to the excess emissions of about 9 million extra trucks on the road.

Nick Mott Wow. 9 million trucks must generate a lot of pollution. Okay, so it's illegal, but is anybody actually getting into trouble for it?

Edward O'Brien In an emailed statement to me, EPA made it clear that the devices that trick emissions control systems are a violation of the Clean Air Act. The agency is expanding its crackdown on companies that sell these things. Since 2020, EPA's fined about 40 device manufacturers and installers. And get this, two Detroit firms that sell and install these "defeat devices" were fined $10 million just this past September.

Nick Mott I wonder what kind of impact that's having on the actual coal-rolling community?

Edward O'Brien Yeah, me too. So I reached out to professional diesel techs and mechanics, social media influencers. Heck, even our listeners, those who responded, declined my formal interview request. But I did have some interesting conversations off mic and noticed an interesting trend.

Nick Mott Yeah. What trend was that?

Edward O'Brien Well, first of all, I think it's important to avoid the temptation to lump everyone in the performance diesel community in the same basket as coal-rollers. There are professional and hobbyist diesel techs and mechanics out there who are obsessed with squeezing gobs of power and every ounce of fuel efficiency out of these engines. Remember, coal-rolling uses a ton of fuel. That's important to understand, especially now that the diesel fuel market is facing the perfect storm of dwindling supply and skyrocketing prices.

Nick Mott So not every diesel enthusiast is into the coal scene.

Edward O'Brien Oh, not at all. Kristina Degele was one of the few people who agreed to an interview.

Kristina Degele We love to be outside, anything that has to do with off-roading mudding, snow-wheeling, camping, fishing, hunting, you name it.

Edward O'Brien Degele and her family live near Alberton, just west of Missoula. We're standing next to her 2004 Ford Excursion Diesel. It is a big and burly 6.0 liter. And while I'm not a car guy, she rattles off a list of what I'm told are some sweet modifications and aftermarket parts. Degele loves this truck, but doesn't use it often for off-roading. She calls it her pavement princess.

Kristina Degele
Edward O'Brien
Kristina Degele

Kristina Degele I don't take her off-roading too much, because when I do that she tends to get stuck.

Edward O'Brien She? Why she?

Kristina Degele I don't know. It's just what I've referred to her as since day one.

Edward O'Brien So as you can see, the Degeles are car people. Coal rollers? Not so much.

Kristina Degele No. We do not have our vehicles tuned in that way. We don't find the need for it.

Edward O'Brien Your message for the guys that do it?

Kristina Degele Why?

I get that you guys want to look cool or for whatever your reason is to roll coal. Just, it's not necessary. Even when somebody is upsetting you with the way they're driving, it's not going to help the situation.

Nick Mott Now we want to know what makes you curious about Montana. This show is all about answering your questions. Send them to us here and find us wherever you listen to podcasts. Thanks for listening.


O’Brien first landed at Montana Public Radio three decades ago as a news intern while attending the University of Montana School of Journalism. His first career job out of school was covering the 1995 Montana Legislature. When the session wrapped up, O’Brien was fortunate enough to land a full-time position at the station as a general assignment reporter. Feel free to drop him a line at
Nick Mott is a reporter and podcast producer based in Livingston, Montana.
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