Where does sludge come from?
Sludge is a thick, sticky residue that can form inside your engine through a combination of combustion by-products (oil oxidation residue, carbon and water). Water condenses as a result of a hot engine cooling down. The oil mixes with the resulting water and forms the thick sludge that sticks to the engine parts. Frequent cold starts and short trips contribute to this condition, by not allowing the engine oil to heat up enough to vaporize and remove the water. Sludge is detrimental in that it can clog key oil passages such as oil drain-back holes and, in some cases, block the oil pick-up screen in the oil pan, causing engine oil starvation (i.e., not enough oil). STP® Oil Additive products contain detergents, which can help suspend sludge in the motor oil, preventing it from accumulating inside your engine.
