Investigation of Modified PIB-Succinimides in Low SAPS Engine Oils

Abstract

Along with the ever stricter economical, technical and mainly environmental regulations new types of low phosphorus, sulphur and metal containing multifunctional lubricant additives are required for formulating so-called low SAPS (Sulphated Ash, Phosphorus and Sulphur) engine oils. In the greatest volume dispersant additives, mainly polyisobuthylene-succinimide types are used in the formulation of engine oils. By structural modification of the dispersants with molybdenum and sulphur containing compounds advantageous complementary effects could be achieved along dispersant efficiency. Various modified PIB-polysuccinimides with complementary antifriction and antiwear (AF/AW), viscosity-index improver and enhanced detergent-dispersant properties were synthesized and investigated both in base oil and engine oil compositions. The detergent-dispersant and the high temperature deposit preventing effects, thermal- and oxidation stability, AF/AW properties and seal compatibility were studied in fully formulated, low SAPS engine oils with reduced zinc-dialkyl-dithiophosphate (ZnDDP) content. Based on the results it was found that by using suitable additive concentrations the conventional dispersant can be advantageously combined or replaced with these new additives to enhance the properties and to reduce the ZnDDP concentration level of the experimental engine oils.