Think ZDDP.
Sulfated Ash, Phosphorus, and Sulfur.
SAPS content is needed to help retain the engine oil’s Total Base Number (TBN), resist viscosity shear loss and thermal breakdown, as well as protect against oxidation, wear, corrosion, and deposit formation; all of which are necessary for extended oil drain intervals.
Sulphated Ash is the amount of metallic content that remains as a result of engine oil combustion. These are mostly derived from the engine oil’s anti-wear and detergent additive chemistry.
Because Sulfated Ash deposits are non-combustible, they cannot be removed by regeneration, and will instead collect in the DPF or other exhaust aftertreatment device.
Too high a concentration of Sulfated Ash will block the DPF, and can cause the engine to lose power and not function properly, and may cause deposits to form on internal engine parts, which can damage the engine.
Phosphorus is an additive, providing anti-wear protection and improving oxidation resistance. The Phosphorus forms a thin layer on metal surfaces, limiting friction of metal parts rubbing together.
Sulfur is also an additive, contributing to overall engine cleanliness, as well as providing anti-wear and antioxidant protection.
Despite their favourable anti-wear and cleanliness properties,
too high a concentration of Phosphorus and Sulfur content can poison and damage a vehicle’s catalyst converter, as well as lead to a buildup of Sulphated Ash in the engine and aftertreatment device.
