Lubricants with calcium-containing detergent and their use for improving low speed pre-ignition

1. A lubricating oil composition comprising:

greater than 50 wt. % of a base oil of lubricating viscosity;

at least 0.3 wt. % of an overbased calcium sulfonate detergent having a total base number of greater than 225 mg KOH/g, measured by the method of ASTM D-2896, and

at least 0.2 wt. % of a low-based/neutral detergent having a total base number of up to 175 mg KOH/g, measured by the method of ASTM D-2896,

wherein a total amount of calcium from the overbased calcium sulfonate detergent and the low-based/neutral detergent ranges from greater than 1100 ppm by weight to less than 2400 ppm by weight based on a total weight of the lubricating oil composition;

a total amount of calcium from the overbased calcium sulfonate detergent is from 900 ppm to 1625 ppm by weight, based on the total weight of the lubricating oil composition; and

a ratio of the ppm of calcium, by weight, provided to the lubricating oil composition by the low-based/neutral detergent to the ppm of calcium, by weight, provided to the lubricating oil composition by the overbased calcium sulfonate detergent, is from 0.08 to 0.4.

2. The lubricating oil composition of claim 1 , wherein the reduction of LSPI events is a 75% or greater reduction and the LSPI events are LSPI counts during 25,000 engine cycles, wherein the engine is operated at 2000 revolutions per minute with brake mean effective pressure of 18,000 kPa.

3. The lubricating oil composition of claim 1 , wherein the low-based/neutral detergent comprises a low-based/neutral calcium-containing detergent.

4. The lubricating oil composition of claim 1 , wherein the low-based/neutral detergent comprises a detergent selected from the group consisting of: a sodium sulfonate, calcium sulfonate detergent and a calcium phenate detergent.

5. The lubricating oil composition of claim 1 , wherein the lubricating oil composition has a ratio of a total mmol metal in the lubricating oil composition to a total base number of the lubricating oil composition ranging from greater than 4.5 to about 10.0.

6. The lubricating oil composition of claim 1 , wherein the lubricating oil composition is effective to pass a TEOST 33 bench oxidation test.

7. The lubricating oil composition of claim 1 , further comprising one or more components selected from the group consisting of friction modifiers, antiwear agents, dispersants, antioxidants, and viscosity index improvers.

8. The lubricating oil composition of claim 1 , wherein the greater than 50% of base oil is selected from the group consisting of Group II, Group III, Group IV, Group V base oils, and a combination of two or more of the foregoing, and wherein the greater than 50 wt. % of base oil is other than diluent oils that arise from provision of additive components or viscosity index improvers in the composition.

9. The lubricating oil composition of claim 1 , wherein a ratio of mmol total metal in the lubricating oil composition to a total base number of the lubricating oil composition is greater than 8 to less than 10 and the lubricating oil composition comprises at least 0.25 wt. % of the low-based/neutral detergent.

10. The lubricating oil composition of claim 2 , wherein the total calcium provided to the lubricating oil composition by the one or more overbased calcium sulfonate detergents is from 1100 ppm to 1625 ppm, by weight, based on the total weight of the lubricating oil composition.

11. The lubricating oil composition of claim 4 , wherein the total calcium provided to the lubricating oil composition by the one or more low-based/neutral calcium-containing detergents is from 50 ppm to 1000 ppm, by weight, based on the total weight of the lubricating oil composition.

12. The lubricating oil composition of claim 1 , wherein the lubricating oil composition is effective to reduce low-speed pre-ignition events in a boosted internal combustion engine lubricated with the lubricating oil composition relative to a number of low-speed pre-ignition events in the same engine lubricated with reference lubricating oil R-1,

wherein R-1 is formulated from about 80.7 wt. % of a Group III base oil, 12.1 wt. % of passenger car motor oil additive package and 7.2 wt. % of a 35 SSI ethylene/propylene copolymer viscosity index improver, wherein the passenger car motor oil additive parka leis an API SN, ILSAC-GF-5, and ACEA A5/B5 qualified DI package and R-1 also showed the following properties and partial elemental analysis:

10.9

Kinematic Viscosity at 100° C. (mm 2 /sec)

3.3

TBS, APPARENT_VISCOSITY, cPa

2438

calcium (ppmw)

<10

magnesium (ppmw)

80

molybdenum (ppmw)

772

phosphorus (ppmw)

855

zinc (ppmw)

9.0

Total Base Number ASTM D-2896 (mg KOH/g)

165

Viscosity Index.

13. A method for reducing low-speed pre-ignition events in a boosted internal combustion engine comprising:

lubricating a boosted internal combustion engine with a lubricating oil composition comprising

greater than 50 wt. % of a base oil of lubricating viscosity;

at least 0.3 wt. % of an overbased detergent having a total base number of greater than 225 mg KOH/g, measured by the method of ASTM D-2896; and

at least 0.2 wt. % of a low-based/neutral detergent having a total base number of up to 175 mg KOH/g, measured by the method of ASTM D-2896; wherein a total amount of calcium from the overbased and low-based/neutral detergent ranges from greater than 1100 ppm by weight to less than 2400 ppm by weight based on a total weight of the lubricating oil composition; and

wherein a total amount of calcium from the overbased detergent is no more than 1800 ppm by weight, based on the total weight of the lubricating oil composition, and

operating the engine lubricated with the lubricating oil composition.

14. The method of claim 13 , wherein the lubricating oil composition passes a TEOST 33 bench oxidation test.

15. The method of claim 14 , wherein LSPI events are based on LSPI counts during 25,000 engine cycles, wherein the engine is operated at 2000 revolutions per minute (RPM) with brake mean effective pressure (BMEP) of 18,000 kPa and the low-speed pre-ignition events in the boosted internal combustion engine lubricated with the lubricating oil composition are reduced relative to a number of low-speed pre-ignition events in the same engine lubricated with reference lubricating oil R-1,

wherein R-1 is formulated from about 80.7 wt. % of a Group III base oil, 12.1 wt. % of passenger car motor oil additive package and 7.2 wt. % of a 35 SSI ethylene/propylene copolymer viscosity index improver, wherein the passenger car motor oil additive package is an API SN, ILSAC-GF-5, and ACEA A5/B5 qualified DI package and R-1 also showed the following properties and partial elemental analysis:

10.9

Kinematic Viscosity at 100° C. (mm 2 /sec)

3.3

TBS, APPARENT_VISCOSITY, cPa

2438

calcium (ppmw)

<10

magnesium (ppmw)

80

molybdenum (ppmw)

772

phosphorus (ppmw)

855

zinc (ppmw)

9.0

Total Base Number ASTM D-2896 (mg KOH/g)

165

Viscosity Index.

16. The method of claim 15 , wherein the low-based neutral detergent comprises a calcium-containing detergent, the overbased detergent comprises a calcium-containing detergent and the overbased detergent provides from about 900 to less than about 1800 ppm by weight calcium to the lubricating oil composition based on a total weight of the lubricating oil composition.

17. The method of claim 13 , wherein a ratio of the ppm of calcium, by weight, provided to the lubricating oil composition by the low-based/neutral detergent to the ppm of calcium, by weight, provided to the lubricating oil composition by the overbased calcium detergent, is from 0.08 to 0.4.

18. The lubricating oil composition of claim 1 , wherein the reduction of LSPI events is a 75% or greater reduction and the LSPI events are LSPI counts during 25,000 engine cycles, wherein the engine is operated at 2000 revolutions per minute with brake mean effective pressure of 18,000 kPa, and wherein the lubricating oil composition is effective to pass a TEOST 33 bench oxidation test.