What is Carbon Build-up? How Does it Affect my Engine? Carbon build-up can be found inside the engine. Over time carbon builds up inside the engine from exhaust and fuel combustion. As the engine burns fuel, the layers of carbon build up causing the valves to stick. This can impede the valves sealing correctly when disposing of exhaust or intaking air into the cylinder. Carbon can also plug up your fuel injector nozzles resulting in poor fuel delivery. For example, when there is a fire in the chimney you can see soot start to build up on the inside walls. This is exactly what is happening inside the engine! Oil travels a long road before it winds up in your vehicle. Gasoline from oil refiners such as Shell, Chevron, etc. mix their gasoline with their own kind of detergents. These detergents are formulated to remove or prevent the carbon build up in the fuel injectors and intake valves. This may differ though with a direct injec ... read more