No, it is generally illegal to sell a car without a catalytic converter ("catless") for on-road use in the United States. Federal law, specifically the Clean Air Act, mandates that all vehicles driven on public roads must have a functioning catalytic converter. This law is enforced by the Environmental Protection Agency (EPA). Selling a catless car as a road-legal vehicle is a violation that can result in significant fines for the seller, often exceeding $10,000. The only legal exception is if the vehicle is sold explicitly as a "for off-road use only" competition vehicle, like a dedicated race car, and this must be clearly stated in the bill of sale. However, this drastically reduces the potential buyer pool and the car's resale value.
The catalytic converter is a critical part of the vehicle's emissions control system. It uses precious metals like platinum, palladium, and rhodium to convert harmful pollutants in the exhaust gas—carbon monoxide, hydrocarbons, and nitrogen oxides—into less harmful substances like carbon dioxide, water, and nitrogen. Removing it increases emissions dramatically and is the primary reason for its legal protection.
Beyond legality, there are practical consequences. A catless car will not pass a state emissions inspection in the many states that require them, making registration renewal impossible. The vehicle will also trigger a "check engine" light due to the missing downstream oxygen sensor data. From a performance perspective, while some believe removing the catalytic converter increases horsepower, modern high-flow cats have minimal restriction, making the power gain negligible for most street applications while creating an excessively loud and often unpleasant exhaust drone.
| Jurisdiction | Potential Fine for Seller | Potential Fine for Installer/Shop | Vehicle Registration Impact |
|---|
| U.S. Federal (EPA) | Up to $4,819 per violation (2023) | Up to $48,192 per violation | N/A |
| California (CARB) | Up to $37,500 per vehicle | Up to $7,500 per day | Cannot register or sell vehicle |
| New York | Up to $22,500 per violation | Up to $22,500 per violation | Failed inspection, registration suspended |
| Texas | Up to $10,000 per day | Up to $10,000 per day | Cannot pass state safety inspection |
| Illinois | Up to $25,000 per violation | Up to $25,000 per violation | Registration denial |
If you have a catless car, your best legal course of action is to have a new, EPA-compliant catalytic converter installed before listing it for sale. This will make the vehicle marketable to the vast majority of buyers and ensure a smooth, legal transaction.
