Method for preventing or reducing low speed pre-ignition

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.

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.