LUBRICANTS WITH ZINC DIALKYL DITHIOPHOSPHATE AND THEIR USE IN BOOSTED INTERNAL COMBUSTION ENGINES

摘要

A lubricating oil composition and method of for providing an acceptable number of low-speed pre-ignition events in a boosted internal combustion engine using the lubricating oil composition. The lubricating oil composition includes greater than 50 wt. % of a base oil of lubricating viscosity, and an additive composition that includes an overbased calcium-containing detergent having a TBN greater than 225 mg KOH/g, and one or more zinc dialkyl dithiophosphate compounds are derived from a molar ratio of secondary alcohol to primary alcohol of 20:100 to about 100:0 and have an average total carbon content of greater than 10 carbon atoms per mole of phosphorous. The lubricating oil compositions contains the overbased calcium-containing detergent in an amount to provide greater than 900 ppm to less than 2400 ppm by weight calcium, and at least 0.01 wt. % of the zinc dialkyl dithiophosphate, both amounts based on the total weight of the lubricating oil composition.