Method and composition for preventing or reducing engine knock and pre-ignition in high compression spark ignition engines

Abstract

A method for preventing or reducing engine knock or pre-ignition in a high compression spark ignition engine lubricated with a lubricating oil by introducing to a combustion chamber of the engine from 0.1 to 5% by volume of the gasoline used a lubricating oil as a formulated oil, said formulated oil having a composition comprising (i) a major amount of a lubricating oil base stock comprising at least 80% by weight of one branched ester having at least 15% of the total carbons in the form of methyl groups, and (ii) a minor amount of at least one ashless amine phosphate antiwear additive. Also provided is a lubricating engine oil for high compression spark ignition engines including (i) a major amount of a lubricating oil base stock comprising at least 80% by weight a trimethylol propane ester of 50:50 mixture of isobutyric acid and 3,5,5-trimethylhexanoic acid and (ii) a minor amount of at least one amine phosphate ashless antiwear additive.

1 . A method for preventing or reducing engine knock or pre-ignition in a high compression spark ignition engine lubricated with a lubricating oil comprising introducing to a combustion chamber of the engine from 0.1 to 5% by volume of the gasoline used a lubricating oil as a formulated oil, said formulated oil having a composition comprising (i) a major amount of a lubricating oil base stock comprising at least 80% by weight of one branched ester having at least 15% of the total carbons in the form of methyl groups, and (ii) a minor amount of at least one ashless amine phosphate antiwear additive. 
     
     
         2 . The method of  claim 1  wherein the formulated oil is an ashless formulated oil. 
     
     
         3 . The method of  claim 1  wherein one branched ester is a branched polyol ester having at least 30% of the total carbons in the form of methyl groups. 
     
     
         4 . The method of  claim 1  wherein the formulated oil further comprises a polymeric aminic antioxidant. 
     
     
         5 . The method of  claim 1  wherein the formulated oil, when 0.1 to 5% by volume of the formulated oil is added to isooctane, the resulting isooctane/formulated oil mixture maintains at least 80% of the isooctane ignition delay or combustion delay per the equipment and test conditions of ASTM D7668. 
     
     
         6 . The method of  claim 1  wherein the one branched ester is present in an amount of from 80 to 99.8 weight percent, based on the total weight of the formulated oil, and the at least one amine phosphate ashless antiwear additive is present in an amount from 0.1 to 4 weight percent, based on the total weight of the formulated oil. 
     
     
         7 . The method of  claim 1  wherein the one branched ester is a dialkyl adipic acid ester having at least 25% of the total alkyl carbons in the form methyl groups. 
     
     
         8 . The method of  claim 7  wherein the dialkyl adipic acid ester is selected from the group consisting of diisopropyl adipate, diisobutyl adipate, diisopentyl adipate, diisohexyl adipate, diisooctyl adipate, diisononyl adipate, diisodecyl adipate, and mixtures thereof. 
     
     
         9 . The method of  claim 1  wherein the one branched ester is a branched polyol ester having at least 40% of the total carbons in the form of methyl groups. 
     
     
         10 . The method of  claim 1  wherein the lubricating oil further comprises one or more other lubricating oil additives selected from the group consisting of antioxidants, detergents, dispersants, antiwear additives, corrosion inhibitors, viscosity modifiers, metal passivators, pour point depressants, seal compatibility agents, antifoam agents, extreme pressure agents, friction modifiers and combinations thereof. 
     
     
         11 . The method of  claim 10  wherein the detergent is an ashless nonionic detergent. 
     
     
         12 . The method of  claim 1  wherein the high compression spark ignition engine has a compression ratio of at least 11. 
     
     
         13 . The method of  claim 1  wherein the high compression spark ignition engine is a super-charged engine or a turbo-charged engine. 
     
     
         14 . The method of  claim 1  wherein the pre-ignition is low speed pre-ignition (LSPI). 
     
     
         15 . The method of  claim 3  wherein the one branched polyol ester is derived from at least one polyhydric alcohol and at least one branched mono-carboxylic acid. 
     
     
         16 . The method of  claim 15  wherein the polyhydric alcohol is selected from the group consisting of neopentyl glycol, 2,2-dimethylol butane, trimethylol ethane, trimethylol propane, trimethylol butane, mono-pentaerythritol, di-pentaerythritol, tri-pentaerythritol, ethylene glycol, propylene glycol and polyalkylene glycols, and mixtures thereof. 
     
     
         17 . The method of  claim 15  wherein the branched mono-carboxylic acid is selected from the group consisting of isobutyric acid, 2,2-dimethyl propionic acid (neopentanoic acid), neoheptanoic acid, neooctanoic acid, neononanoic acid, iso-hexanoic acid, neodecanoic acid, 2-ethyl hexanoic acid (2EH), 3,5,5-trimethyl hexanoic acid (TMH), isoheptanoic acid, isooctanoic acid, isononanoic acid, isodecanoic acid, and mixtures thereof. 
     
     
         18 . The method of  claim 15  wherein the one branched polyol ester of at least one branched mono-carboxylic acid comprises a mono-pentaerythritol ester of at least one branched mono-carboxylic acid or, a di-pentaerythritol ester of at least one branched mono-carboxylic acid. 
     
     
         19 . The method of  claim 15  wherein the one branched polyol ester of at least one branched mono-carboxylic acid comprises a trimethylol propane ester of 50:50 mixture of isobutyric acid and 3,5,5-trimethylhexanoic acid. 
     
     
         20 . A lubricating engine oil for high compression spark ignition engines comprising (i) a major amount of a lubricating oil base stock comprising at least 80% by weight a trimethylol propane ester of 50:50 mixture of isobutyric acid and 3,5,5-trimethylhexanoic acid and (ii) a minor amount of at least one amine phosphate ashless antiwear additive. 
     
     
         21 . The lubricating engine oil of  claim 20  which is an ashless lubricating engine oil. 
     
     
         22 . The lubricating engine oil of  claim 20  further comprising an aminic antioxidant. 
     
     
         23 . The lubricating engine oil of  claim 20  further comprising a polymeric aminic antioxidant. 
     
     
         24 . The lubricating engine oil of  claim 20  further comprising one or more other lubricating oil additives selected from the group consisting of antioxidants, detergents, dispersants, antiwear additives, corrosion inhibitors, viscosity modifiers, metal passivators, pour point depressants, seal compatibility agents, antifoam agents, extreme pressure agents, friction modifiers and combinations thereof. 
     
     
         25 . The lubricating engine oil of  claim 24  wherein the detergent is an ashless nonionic detergent. 
     
     
         26 . The lubricating engine oil of  claim 20  wherein the high compression spark ignition engine has a compression ratio of at least 11. 
     
     
         27 . The lubricating engine oil of  claim 20  wherein the high compression spark ignition engine is a super-charged engine or a turbo-charged engine. 
     
     
         28 . The lubricating engine oil of  claim 20  wherein the pre-ignition is low speed pre-ignition (LSPI).