Eventually the PTFE buildup within the engine can clog oil ports or passages and end up as a sludge-like material in the engine. This clogging may cause serious damage to bearings, oil pumps etc. and may cause premature engine failures. Soft metals in lubricant additives include copper, zinc and lead are advantageous because they fill imperfections and pores in the machined surfaces to create a smoother surface. These metal particles are not dissolved in the oil but are suspended there and are still foreign metal particles. As the engine rotates, friction generates a static electricity charge.
Most metals are conductors of electricity.
Certain metals such as zinc and lead will become magnetically polarized as this charge of static electricity discharges through the oil with metals added. These magnetically charged metal particles will adhere to the metal surfaces of the internal engine parts creating a metallic buildup. In this condition, they are an abrasive and may cause extra wear and premature engine failure. Solvents as lubricant additives are advertised to help clean your engine. They indeed help remove carbon and sludge deposits because they are solvents.