the present invention provides a low phosphorus lubricating oil composition containing a mixture of zinc dithiophosphates in a certain ratio surprisingly yields improved lead corrosion . the synergistic combination of mixed zinc dithiophosphates containing a zinc primary dialkyl dithiophosphate , zinc secondary dialkyl dithiophosphate and zinc diaryl dithiophosphate in a respective ratio , based on the phosphorus content , of the zinc primary dialkyl dithiphosphate to zinc secondary dialkyl dithiophosphate from about 2 : 1 to about 1 : 2 and the ratio of the mixture of zinc primary dialkyl dithiophosphate and zinc secondary dialkyl dithiophosphate to zinc diaryl dithiophosphate from about 6 : 1 to about 1 : 1 . when used in a lubricating oil composition having a total phosphorus content less than about 0 . 06 wt %, based on the total weight of the lubricating oil composition to lubricate internal combustion engines . the mixture of zinc dithiophosphates greatly reduces lead corrosion .