Lubricants with overbased calcium and overbased magnesium detergents and methods for improving low-speed early ignition

摘要

This disclosure relates to lubricating oil compositions and methods of operating a powered internal combustion engine. The lubricating oil contains more than 50% by weight of base oil, one or more overbased calcium-containing detergents, one or more overbased magnesium-containing detergents, and one or more molybdenum compounds, and has an LSPI of 60% or more compared to the LSPI of the reference lubricant. Results in a decrease, and passes the ball rust test. The ratio of weight percent of calcium from overbased detergent to weight percent of magnesium from overbased detergent is less than 11.9. The ratio of total ppm of magnesium to total TBN in mg KOH / g of lubricant is greater than 19. The ratio of total ppm of calcium to total TBN of the lubricant is less than 222. The oils and methods of the present invention can reduce low-speed pre-ignition events in back-powered internal combustion engines compared to commercially available lubricants.