Lubricating oil compositions and use thereof for improving journal bearing wear in internal combustion engines

Abstract

This invention relates to a lubricating oil composition comprising or resulting from the admixing of: (i) base oil, (ii) an overbased calcium based detergent at treat level to deliver between 500 to 1300 ppm by weight of calcium to the composition; (iii) an overbased magnesium based detergent at treat level to deliver between 500 to 1300 ppm by weight of magnesium to the composition; wherein the total weight of combined calcium and magnesium in the composition ranges from 1000 ppm to 1800 ppm. The composition has a total sulfated ash of less than or equal to 1.0 wt. %, a high temperature high shear viscosity at 150° C. of greater than or equal to 1.8 mPa·s and less than or equal to 2.9 mPa·s, and a total phosphorous level of less than or equal to 0.080 wt. %. The inventive composition provides a 5% to 60% decrease in journal bearing wear as measured by maximum average wear in microns using the TE-92 start/stop test method compared to a lubricating oil composition of comparable HTHS, but not including the mixture of the overbased calcium based detergent and the overbased magnesium based detergent. Also provided are a method of decreasing journal bearing wear in an internal combustion engine and a method of making the lubricating oil composition.