Engine Lubricant Using Molybdenum Dithiocarbamate As an Antioxidant Top Treatment in High Sulfur Base Stocks
Publication Date: 2001-May-14
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The present invention provides: . A composition comprising: (a) a major amount of an API Group I mineral oil base stock, wherein said base stock contains at least 300 ppm sulfur; (b) a molybdenum dithiocarbamate in an amount suitable to provide about 50 to about 600 ppm molybdenum to the composition; (c) a succinimide dispersant having a polyolefin backbone, where the polyolefin has a number average molecular weight greater than about 1500; (d) a zinc dialkyldithiophosphate derived from at least one secondary alcohol; and (e) at least one oxidation inhibitor selected from the group consisting of hindered phenols, alkylated aromatic amines, and sulfurized olefins. . A method for inhibiting oxidation in high sulfur API Group I base stocks, comprising the following steps: (a) treating said base stock with an additive package which is capable of passing a Sequence IIIF test when formulated in Group II base stocks; and (b) adding thereto a molybdenum dithiocarbamate in an amount sufficient to deliver about 50 to about 600 ppm of molybdenum to the finished lubricating oil.