What are Wisconsin Car Exhaust Laws?

In Wisconsin, car exhaust laws are covered under the state’s environmental regulations, specifically through the Department of Natural Resources (DNR). These laws aim to control and regulate the amount of pollution that is being emitted by vehicles in the state. The rules primarily focus on the exhaust system, which plays a significant role in an automobile’s emissions and noise levels.

Wisconsin’s Vehicle Noise Regulations

One of the primary concerns surrounding vehicle exhaust is its noise levels. Under Wisconsin law, there are certain noise limits that vehicles, including their exhaust systems, must stay within when traveling on public roads. These laws dictate the maximum amount of noise a vehicle’s engine can produce, as well as the maximum amount of sound the vehicle’s horn and other audible warnings can create.

In Wisconsin, vehicles that exceed these noise limits can face penalties that range from citations and fines to impoundment and even forfeiture of the vehicle. Therefore, it is essential for drivers to ensure their vehicles meet the state’s noise standards before driving on public roads.

Wisconsin’s Vehicle Emissions Regulations

Another primary focus of Wisconsin’s car exhaust laws is reducing the amount of pollution caused by vehicle emissions. To achieve this, the state has set specific limits on the amount of certain pollutants a vehicle can emit through its exhaust system. These pollutants include nitrogen oxides, carbon monoxide, and particulate matter.

Wisconsin requires all vehicles to undergo emissions tests before they can receive license plates. Testing is conducted annually for vehicles that are five years old or newer, and every two years for vehicles older than five years. Vehicles that fail the emissions test will not receive a license plate until they pass, which can lead to additional inspection and repair expenses.

Illegal Car Exhaust Systems in Wisconsin

In Wisconsin, it is illegal to use exhaust systems that produce excessive noise or excessive pollution. This includes mufflers and exhaust systems that have been modified or altered in a way that increases noise or pollution levels. Wisconsin law also prohibits the use of straight pipes and gutted mufflers, which are exhaust systems that have been modified to remove internal baffling and sound-dampening material.

Vehicles equipped with illegal exhaust systems can face fines and other penalties, which can include impoundment and forced removal of the exhaust system. It is essential to ensure that any modifications made to a vehicle’s exhaust system comply with Wisconsin law to avoid these penalties.

Penalties for Violating Wisconsin Car Exhaust Laws

Violations of Wisconsin’s car exhaust laws can lead to a range of penalties, depending on the severity and frequency of the offense. Minor violations, such as a noisy muffler, may result in a simple citation and fine. More severe violations, such as illegal exhaust modifications or multiple emissions test failures, can lead to impoundment and other consequences.

Vehicle owners should be aware of the potential penalties for violating these laws, as well as their rights to appeal or contest any citations or fines that they may receive.


Wisconsin’s car exhaust laws aim to regulate the amount of pollution and noise generated by vehicles on public roads, with the primary concern being the exhaust system. Drivers must ensure that their vehicles comply with all state regulations regarding noise limits, emissions limits, and the use of legal exhaust systems. In doing so, they can avoid fines and other penalties while also helping to reduce the pollution caused by their vehicles.


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