Method of improving the oxidative stability of a lubricating composition

Abstract

Method of improving the oxidative stability of a lubricating composition which is used to lubricate a spark ignition internal combustion engine, the spark-ignition engine being comprised within the powertrain of a hybrid electric vehicle, wherein the method comprises the step of introducing into the combustion chamber of the spark-ignition engine a gasoline composition wherein the gasoline composition comprises a hydrocarbon base fuel containing 10 to 20% v olefins, not greater than 5% v olefins of at least 10 carbon atoms, and not greater than 5% v aromatics of at least 10 carbon atoms, based on the base fuel, initial boiling point in the range 30 to 40° C., T10 in the range 45 to 57° C., T50 in the range 82 to 104° C., T90 in the range 140 to 150° C. and final boiling point not greater than 220° C.

1 . A method of improving the oxidative stability of a lubricating composition which is used to lubricate a spark ignition internal combustion engine, the spark-ignition engine being comprised within the powertrain of a hybrid electric vehicle, wherein the method comprises the step of introducing into the combustion chamber of the spark-ignition engine a gasoline composition wherein the gasoline composition comprises a hydrocarbon base fuel containing 10 to 20% v olefins, not greater than 5% v olefins of at least 10 carbon atoms, and not greater than 5% v aromatics of at least 10 carbon atoms, based on the base fuel, initial boiling point in the range 30 to 40° C., T10 in the range 45 to 57° C., T50 in the range 82 to 104° C., T90 in the range 140 to 150° C. and final boiling point not greater than 220° C. 
     
     
         2 . The method according to  claim 1  wherein the gasoline composition contains 0 to 10% v of at least one oxygenate selected from methanol, ethanol, isopropanol and isobutanol. 
     
     
         3 . The method according to  claim 1  wherein the hydrocarbon base fuel contains 10 to 20% v olefins. 
     
     
         4 . The method according to  claim 1  wherein the hydrocarbon base fuel contains 12 to 18% v olefins. 
     
     
         5 . The method according to  claim 1  wherein the base fuel has initial boiling point in the range 28 to 42° C., T 10  in the range 42 to 58° C., T 50  in the range 80 to 105° C., T 90  in the range 135 to 170° C. and final boiling point not greater than 200° C. 
     
     
         6 . The method according to  claim 1  wherein the base fuel has initial boiling point in the range 30 to 40° C., T10 in the range 45 to 57° C., T50 in the range 82 to 104° C., T90 in the range 140 to 150° C., and final boiling point not greater than 180° C. 
     
     
         7 . The method according to  claim 1  wherein the gasoline composition contains up to 10% v of ethanol. 
     
     
         8 . The method according to  claim 1  wherein the fuel composition comprises one or more antioxidants. 
     
     
         9 . The method according to  claim 1  wherein the lubricating composition comprises an antioxidant of the hindered phenol type. 
     
     
         10 . The method according to  claim 1  wherein the hybrid electric vehicle is a plug-in hybrid electric vehicle. 
     
     
         11 . A gasoline composition suitable for use as a fuel for a spark-ignition engine for improving oxidative stability of engine crank case lubricant and/or for reducing frequency of engine lubricant changes, wherein the spark-ignition engine is comprised in the powertrain of a hybrid electric vehicle, wherein the gasoline composition comprises a hydrocarbon base fuel containing 10 to 20% v olefins, not greater than 5% v olefins of at least 10 carbon atoms, and not greater than 5% v aromatics of at least 10 carbon atoms, based on the base fuel, initial boiling point in the range 30 to 40° C., T10 in the range 45 to 57° C., T50 in the range 82 to 104° C., T90 in the range 140 to 150° C. and final boiling point not greater than 220° C.