Method for preventing or reducing low speed pre-ignition

Abstract

A method for preventing or reducing low speed pre-ignition in an engine lubricated with a lubricating oil by using as the lubricating oil a formulated oil. The formulated oil has a composition including a lubricating oil base stock as a major component, and at least one detergent, as a minor component. The detergent includes at least one alkaline earth metal salt of an organic acid, and the at least one alkaline earth metal salt of an organic acid comprises at least one magnesium salt of an organic acid. A lubricating engine oil having a composition including a lubricating oil base stock as a major component; and at least one detergent, as a minor component. The lubricating oils of this disclosure are particularly advantageous as passenger vehicle engine oil (PVEO) products.

What is claimed is: 
     
         1 . A method for preventing or reducing low speed pre-ignition in an engine lubricated with a lubricating oil by using as the lubricating oil a formulated oil, said formulated oil having a composition comprising a lubricating oil base stock as a major component; and at least one detergent, as a minor component; wherein said detergent comprises at least one alkaline earth metal salt of an organic acid, and said at least one alkaline earth metal salt of an organic acid comprises at least one magnesium salt of an organic acid; and wherein the engine exhibits greater than 50% reduced low speed pre-ignition, based on normalized low speed pre-ignition (LSPI) counts per 25,000 engine cycles, engine operation at 2000 revolutions per minute (RPM) and brake mean effective pressure (BMEP) at 18 bar, as compared to low speed pre-ignition performance achieved in an engine using a lubricating oil that does not comprise at least one magnesium salt of an organic acid. 
     
     
         2 . The method of  claim 1  wherein the minor component further comprises at least one zinc-containing compound or at least one antiwear agent, wherein said at least one antiwear agent comprises at least one zinc dialkyl dithiophosphate compound derived from a secondary alcohol. 
     
     
         3 . The method of  claim 1  wherein the minor component further comprises at least one zinc-containing compound or at least one antiwear agent, and at least one boron-containing compound, wherein said at least one antiwear agent comprises at least one zinc dialkyl dithiophosphate compound derived from a secondary alcohol, and said boron-containing compound comprises at least one borated dispersant, or a mixture of a boron-containing compound and a non-borated dispersant. 
     
     
         4 . The method of  claim 1  wherein the lubricating oil base stock comprises a Group I, Group II, Group III, Group IV, or Group V base oil. 
     
     
         5 . The method of  claim 4  wherein the Group V base oil comprises an ester base oil in a concentration of 2% to 20% and having a kinematic viscosity at 100° C. of 2 cSt to 8 cSt, and the Group III base oil comprises a GTL base oil. 
     
     
         6 . The method of  claim 1  wherein the alkaline earth metal salt of an organic acid is selected from the group consisting of an alkaline earth metal sulfonate, an alkaline earth metal carboxylate, an alkaline earth metal phenate, an alkaline earth metal phosphate, and mixtures thereof. 
     
     
         7 . The method of  claim 1  wherein the detergent comprises (i) at least one of magnesium sulfonate, magnesium phenate, and magnesium salicylate, and mixtures thereof, and optionally at least one of calcium sulfonate, calcium phenate, and calcium salicylate, and mixtures thereof; (ii) at least one magnesium salt of an organic acid which is selected from magnesium sulfonate, magnesium salicylate, magnesium carboxylate, magnesium phenate, magnesium phosphate, and mixtures thereof; or (iii) magnesium sulfonate, a mixture of magnesium sulfonate and magnesium salicylate, a mixture of magnesium sulfonate and magnesium phenate, or a mixture of magnesium sulfonate and magnesium carboxylate. 
     
     
         8 . The method of  claim 7  wherein, in a detergent comprising a mixture of a magnesium salt of an organic acid and a calcium salt of an organic acid, the detergent ratio of magnesium metal to calcium metal ranges from 1:0 to 1:10. 
     
     
         9 . The method of  claim 1  wherein (i) magnesium and alkaline earth metal contributed by the detergent is present in the lubricating oil in an amount from 500 ppm to 5000 ppm; (ii) total base number (TBN), as measured by ASTM D2896, contributed by the detergent ranges from 2 mg KOH/g to 17 mg KOH/g; or (iii) sulfated ash contributed by the detergent ranges from 0.4 to 1.7 wt %. 
     
     
         10 . The method of  claim 1  wherein the detergent concentration ranges from 1.0 to 6.0 weight percent, based on the total weight of the lubricating oil. 
     
     
         11 . The method of  claim 1  wherein the engine exhibits greater than 75% reduced low speed pre-ignition, based on normalized low speed pre-ignition (LSPI) counts per 25,000 engine cycles, engine operation at 2000 revolutions per minute (RPM) and brake mean effective pressure (BMEP) at 18 bar, as compared to low speed pre-ignition performance achieved in an engine using a lubricating oil containing a minor component other than the at least one detergent, and in an amount other than the amount of the at least one detergent, in the lubricating oil. 
     
     
         12 . The method of  claim 2  wherein the zinc-containing compound is selected from the group consisting of zinc carboxylate, zinc sulfonate, zinc acetate, zinc napthenate, zinc alkenyl succinate, zinc acid phosphate salt, zinc phenate, and zinc salicylate. 
     
     
         13 . The method of  claim 2  wherein the zinc dialkyl dithiophosphate compound is represented by the formula
   Zn[SP(S)(OR 1 )(OR 2 )] 2    
 wherein R 1  and R 2  are independently primary or secondary C 1  to C 8  alkyl groups, provided at least one of R 1  and R 2  is a secondary C 1  to C 8  alkyl group. 
 
     
     
         14 . The method of  claim 13  wherein the primary or secondary C 1  to C 8  alkyl groups of the zinc dialkyl dithiophosphate compound are derived from an alcohol selected from the group consisting of: 2-propanol, 1-butanol, 1-isobutanol (1-i-C4), 2-butanol (2-C4), 1-pentanol (primary C-5), 3-methyl-1-butanol (primary C-5), 2-pentanol (C5), 3-pentanol (C5), 3-methyl-2-butanol (C5), 1-hexanol (primary C6), 4-methyl-1-pentanol (primary C6), 4-methyl-2-pentanol (C6), and 2-ethyl-1-hexanol (primary C8), and mixtures thereof. 
     
     
         15 . The method of  claim 13  wherein the zinc dialkyl dithiophosphate compound is derived at least in part from (i) a C 3  to C 8  secondary alcohol, or a mixture thereof; or (ii) a mixture of a C 1  to C 8  primary alcohol and a C 1  to C 8  secondary alcohol. 
     
     
         16 . The method of  claim 2  wherein (i) zinc content contributed by the zinc-containing compound or antiwear agent in the lubricating oil ranges from 500 ppm to 2000 ppm; (ii) phosphorus content contributed by the zinc-containing compound or antiwear agent compound in the lubricating oil ranges from 400 ppm to 2000 ppm; (iii) zinc to phosphorus ratio in the lubricating oil ranges from 1.0 to 2.0; or (iv) the ratio of total metals provided by the detergent to total metals provided by the zinc-containing compound and antiwear agent is 0.8 to 4.8. 
     
     
         17 . The method of  claim 2  wherein the zinc-containing compound or antiwear agent concentration ranges from 0.5 to 5.0 weight percent, based on the total weight of the lubricating oil. 
     
     
         18 . The method of  claim 2  wherein the engine exhibits greater than 75% reduced low speed pre-ignition, based on normalized low speed pre-ignition (LSPI) counts per 25,000 engine cycles, engine operation at 2000 revolutions per minute (RPM) and brake mean effective pressure (BMEP) at 18 bar, as compared to low speed pre-ignition performance achieved in an engine using a lubricating oil containing a minor component other than the at least one detergent and the at least one zinc-containing compound or antiwear agent, and in an amount other than the amount of the at least one detergent and the at least one zinc-containing compound or antiwear agent, in the lubricating oil. 
     
     
         19 . The method of  claim 3  wherein the boron-containing compound or borated dispersant is selected from the group consisting of a borated succinimide, a borated succinate ester, a borated succinate ester amide, a borated Mannich base, and mixtures thereof; and the non-borated dispersant comprises a succinic anhydride derived succinimide or succinate ester with a coupling agent, wherein the coupling agent comprises a boron-containing compound. 
     
     
         20 . The method of  claim 3  wherein boron is provided to the lubricating oil by a mixture of an organic or inorganic boron-containing compound and a borated succinimide, and/or a boron-containing compound and a hydrocarbyl succinimide and/or a borated succinimide, a borated succinate ester, a borated succinate ester amide, a Mannich base, or mixtures thereof; wherein the borated succinimide is a mono succinimide, bis-succinimide, or a mixture thereof. 
     
     
         21 . The method of  claim 3  wherein the ratio of total zinc from the zinc-containing compound and antiwear agent plus total alkaline earth metal from the detergent divided by the total boron from the boron-containing compound and borated dispersant, in the lubricating oil, is 9.2 to 45. 
     
     
         22 . The method of  claim 3  wherein the boron-containing compound and borated dispersant concentration ranges from 0.1 to 20 weight percent, based on the total weight of the lubricating oil. 
     
     
         23 . The method of  claim 3  wherein the engine exhibits greater than 75% reduced low speed pre-ignition, based on normalized low speed pre-ignition (LSPI) counts per 25,000 engine cycles, engine operation at 2000 revolutions per minute (RPM) and brake mean effective pressure (BMEP) at 18 bar, as compared to low speed pre-ignition performance achieved in an engine using a lubricating oil containing a minor component other than the at least one detergent, the at least one zinc-containing compound or antiwear agent and the at least one boron-containing compound, and in an amount other than the amount of the at least one detergent, the at least one zinc-containing compound or antiwear agent, and the at least one boron-containing compound, in the lubricating oil. 
     
     
         24 . The method of  claim 1  wherein the lubricating oil further comprises one or more of a viscosity index improver, antioxidant, pour point depressant, corrosion inhibitor, metal deactivator, seal compatibility additive, anti-foam agent, inhibitor, anti-rust additive, and friction modifier. 
     
     
         25 . The method of  claim 1  wherein the lubricating oil is used as a passenger vehicle engine oil (PVEO) or a natural gas engine oil. 
     
     
         26 . A lubricating engine oil having a composition comprising a lubricating oil base stock as a major component; and at least one detergent, as a minor component; wherein said detergent comprises at least one alkaline earth metal salt of an organic acid, and said at least one alkaline earth metal salt of an organic acid comprises at least one magnesium salt of an organic acid; and wherein the engine exhibits greater than 50% reduced low speed pre-ignition, based on normalized low speed pre-ignition (LSPI) counts per 25,000 engine cycles, engine operation at 2000 revolutions per minute (RPM) and brake mean effective pressure (BMEP) at 18 bar, as compared to low speed pre-ignition performance achieved in an engine using a lubricating oil that does not comprise at least one magnesium salt of an organic acid. 
     
     
         27 . The lubricating engine oil of  claim 26  wherein the minor component further comprises at least one zinc-containing compound or at least one antiwear agent, wherein said at least one antiwear agent comprises at least one zinc dialkyl dithiophosphate compound derived at least in part from a secondary alcohol. 
     
     
         28 . The lubricating engine oil of  claim 26  wherein the minor component further comprises at least one zinc-containing compound or at least one antiwear agent, and at least one boron-containing compound, wherein said at least one antiwear agent comprises at least one zinc dialkyl dithiophosphate compound derived from a secondary alcohol, and said boron-containing compound comprises at least one borated dispersant, or a mixture of a boron-containing compound and a non-borated dispersant. 
     
     
         29 . An engine lubricated with the lubricating engine oil of  claim 26 . 
     
     
         30 . A method for preventing or reducing low speed pre-ignition in an engine lubricated with a lubricating oil by using as the lubricating oil a formulated engine oil, said formulated engine oil having a composition comprising at least one lubricating oil base stock at from 70 to 85 wt. %; and at least one detergent at a loading to contribute from 300 to 3200 ppm of magnesium metal to the formulated engine oil; wherein said at least one detergent comprises at least one alkaline earth metal salt of an organic acid, and said at least one alkaline earth metal salt of an organic acid comprises at least one magnesium sulfonate, wherein the engine exhibits greater than 50% reduced low speed pre-ignition, based on normalized low speed pre-ignition (LSPI) counts per 25,000 engine cycles, engine operation at 2000 revolutions per minute (RPM) and brake mean effective pressure (BMEP) at 18 bar as compared to low speed pre-ignition performance achieved in an engine using a lubricating oil that does not include the at least one magnesium sulfonate and does include at least one calcium salt of an organic acid. 
     
     
         31 . The method of  claim 30  wherein the formulated engine oil comprises SAE 0W-X or 5W-X wherein X is selected from the group consisting of 8, 12, 16, 20, 30, and 40. 
     
     
         32 . The method of  claim 30  wherein the at least one lubricating oil base stock has a kinematic viscosity ranging from 3.5 cSt to 6.0 cSt at 100 C. 
     
     
         33 . The method of  claim 30  wherein the formulated engine oil has a TBN of 4 to 10 and exhibits substantial elimination of LSPI. 
     
     
         34 . The method of  claim 30  wherein the formulated engine oil has a TBN of 10 to 20 and exhibits a LSPI reduction of at least 50%. 
     
     
         35 . The method of  claim 30  wherein the formulated engine oil includes an ash level of from 0.2 to 1.0 wt. % and exhibits a substantial elimination of LSPI. 
     
     
         36 . The method of  claim 30  wherein the formulated engine oil includes an ash level of from 1.0 to 2.0 wt. % and exhibits a LSPI reduction of at least 50%.