A factory BMW 635csi exhaust is the most dependable way for your sedan to collect and remove fumes from its engine cylinders and combustion chamber. It's designed to clean and release these fumes in gaseous form, far enough away from the car, muffling operational noise in the process. That keeps emissions harmful to you from making you sick, and it's better for the environment than pure exhaust gas. Exhaust systems have five basic parts. The catalytic converter, or cat, uses reactive chemicals to convert toxic substances into carbon dioxide and water vapor. The exhaust manifold pulls exhaust gas from each cylinder and passes it through the exhaust pipe. Your muffler and resonator both minimize engine noise while making the most of exhaust airflow and optimizing fuel economy. Your muffler's tail pipe is where the process ends. It sends exhaust fumes out of your car and disperses them into the air. When to replace an exhaust system varies. Your catalytic converter typically lasts about 100,000 miles, depending on how and where you drive. Mufflers and resonators last anywhere from 2 to 4 years. Either way, there are signs and symptoms of exhaust problems you can look for. They include a lit-up Check Engine light, worsening fuel economy, strange noises from your exhaust pipe or muffler, and even a rotten egg smell, which indicates improperly cleaned fumes. Luckily, if you need a genuine replacement BMW 635csi exhaust, our local auto parts department can help. We've got a great selection, and you can order online, direct from the OEM, right through us. Buy now we'll ship quickly!