What Does Rolling Coal Mean?  Is It Illegal To Roll Coal?

You may have seen these big diesel trucks driving down the road spewing diesel from their exhaust and wondering if there was something wrong with the truck.  While it’s normal to see some exhaust gases coming from a diesel car or truck, rolling coal increases the amount of exhaust to a whole new level.

Rolling coal is the process of modifying a diesel engine to increase the amount of fuel entering the engine which increases the amount of exhaust smoke coming out of the exhaust.  

You may be wondering why people would want to do this or if it’s illegal to modify your truck to do this.  While rolling coal is not outright illegal in most states you can still be pulled over for rolling coal.  Let me explain.

Is Rolling Coal Illegal?

In most states rolling coal is going to be illegal in one way or another.  Depending on what state or country you live in there may also be emissions testing that is required yearly.  I live in the US in Indiana and currently, there is no vehicle inspections or requirement for emissions testing in Indiana.

This allows some people to modify their engines to roll coal but it’s not really all that common in the city that I live in.  In smaller cities, it’s more common to see trucks rolling coal.

That doesn’t mean that it is legal to roll coal in Indiana and you won’t have any problems with the cops.  In most states, it’s illegal to tamper with the exhaust of your car or to remove any parts of the exhaust responsible for reducing or eliminating emissions.  This is also true in Indiana.

So while you may be able to get away with rolling coal in your truck you can still get pulled over by your local police or state trooper for rolling coal.

Is Rolling Coal Bad For The Environment?

Yes, rolling coal is bad for the environment because of the added exhaust fumes that are output to the environment.  Vehicle manufacturers are mandated by the Environmental Protection Agency (EPA) to only let their vehicles emit a certain amount of exhaust gases to the environment.  This is because exhaust gases can be very harmful to the environment.

Exhaust gases contain particulate matter and NOx emissions that are harmful to the environment as well as humans.  NOx emissions are caused by the reaction of Nitrogen and Oxygen during the combustion process.  Modifying your engine to roll coal increases the amount of NOx gases emitted and which has adverse health effects in humans as well and can cause acid rain as well as smog in higher concentrations.

This is why states like California have vehicle inspections and emissions testing to see how much NOx your car is outputting.  If you modify your engine to roll coal you likely will not pass a vehicle inspection unless you have the ability to reset your engine back to the factory tune.

Is Rolling Coal Bad For Your Truck?

Rolling coal can be bad for your truck and your wallet over time because of the increased exhaust gases emitted by the truck’s engine.  To roll coal the truck’s engine will need to be modified to increase the amount of fuel injected into the pistons of your engine.

As more fuel is dumped into your engine this will reduce the gas mileage of your truck.  The more fuel that your engine uses the more gas you will need to get around, which will ultimately cost you more money in the long run as you will have to fill up your truck with fuel more often.

Excess exhaust gases can also be bad for the sensors in your exhaust.  Cars and trucks will typically have sensors that are mounted inside of the exhaust to monitor how much air and fuel is leaving the engine so that the air and fuel mixture can be modified to either increase or decrease the amount of fuel that is injected into the engine.

A diesel engine modified to roll coal will either need to have these sensors removed or can expect to always have a check engine light on the dash.  With the O2 sensors still installed the truck will know that excess fuel is being dumped into the engine and try to reduce the amount of fuel being injected.

I would suspect that most people that modify their truck to roll coal will remove their O2 sensors from the exhaust or tune their truck to not use them so that their check engine lights weren’t on all the time.

Is Rolling Coal Bad For A Diesel Engine?

Rolling coal will not be bad for a diesel engine it will just cause the engine to burn more fuel.  Diesel fuel will actually clean the inside of your engine as it’s injected into the cylinders of an engine and eventually out through the exhaust valves of your engine.  So you could make the argument that rolling coal can actually be better for your engine.

However, you should expect the gas mileage of an engine modified to roll coal to be way worse.  Rolling coal may not be bad for your diesel engine but it may have an effect on your pocketbook.

If you’d like to learn more about things you can do to increase your gas mileage check out my other article for 12 tips to increase your MPG.

Is Rolling Coal Illegal In California?

Yes, rolling coal is illegal in California.  If you’ve modified your truck to allow you allow you to roll coal you likely will not be able to pass an emissions test in the state of California.  So if you are just visiting California then this may not be an issue for you as long as your home state doesn’t do emissions testing.  However, you can still get a ticket in California for rolling coal.

Excessive exhaust gases can be a safety hazard because they obstruct the roadway and your ability to see down it.  If you’ve ever been behind a semi-truck belching large plumes of exhaust gas you know how much exhaust can obstruct the roadway.  Do you think that diesel exhaust gas is good to breathe in?

Is Rolling Coal Illegal in the United States?

Each state in the US has its own laws regarding cars and emissions.  However, in most states, it’s illegal to roll coal because the exhaust and emissions equipment has been modified or removed to allow the truck to roll coal which is a violation of the Clean Air Act implemented by the EPA.

While most states don’t have any laws specifically banning rolling coal that doesn’t mean that it’s legal.  You can still be pulled over for obstructing the roadway with excessive exhaust fumes, which can create a safety hazard.

To see the full list of states that prohibit rolling coal Wikipedia has a page that details the laws for each state and in which states it’s illegal to roll coal.

Why Do People Roll Coal?

A lot of people that roll coal are just looking for attention from their fellow motorists.  Some people that modify their trucks to roll coal are specifically doing it to protest electric and hybrid vehicles.

There are plenty of videos online showing people rolling coal on Tesla cars and Toyota Priuses.  These people rolling coal think that they are being funny in protest of the EV or hybrid cars but in reality, are only annoying other motorists.