Black soot is forming on the rear passenger side fender by the exhaust. I have checked the air filter and that is clean. What else should I look for or what should I tell my mechanic to look for first or any thoughts? I’ve been using regular unleaded gas.I have a 2023 Chevy Silverado 2500.

 

Black sooty exhaust are signs of an engine that is running poorly - either running too rich, or burning oil I would think. I drive a white 2006 Silverado, and have never to this day seen any sooty deposits on the paint near the exhaust. Does this happen all the time, or just when you've been towing or hauling a heavy load?

I would talk to your dealer about this, since the vehicle should certainly be under warranty.