Diesel crankcase lubricant composition

A lubricating oil composition characterized by the absence therefrom of a silver friction modifier as well as by improved alkaline retention, silver corrosion protection and percent viscosity increase comprising a hydrocarbon oil of lubricating viscosity containing:

• an alkenyl succinimide detergent-dispersant, a pour depressant and from 0.1 to 90 weight percent of a non-CO.sub.2 blown 2:1 calcium hydroxide overbased calcium sulfurized alkylphenol having an alkylphenol to calcium metal ratio of about 2 to 3 , produced by the steps of:
• (a) overbasing at a temperature between about 350.degree.and 425.degree. F. under a pressure not exceeding 10 psig with from about 1.8 to 2.2 moles of a calcium alkoxyalkoxide of the formula:
• Ca(O--A--OR').sub.2
• where A is alkanediyl of from 1 to 6 carbons and R' is alkyl of from 1 to 25 carbons, a sulfurized calcium alkylphenolate having a calcium content between about 1 and 8.0 weight percent which has the formula:
• ##STR3## wherein R, R' and A are as shown above;
• x ranges from about 1 to 4, y ranges from 0 to 1.0 and z ranges from 0 to 0.1;
• (b) sparging the resulting mixture with an inert gas substantially at the above temperature;
• (c) steaming the sparged mass again at substantially the said temperature;
• (d) repeating said sparging with said gas at an increased stripping rate, continued for about two hours at about 350.degree. F.;
• (e) adding a diluent oil;
• (f) adding a filter aid to the reaction mass, and
• (g) separating a product having the above formula wherein z ranges from 1.8 to 2.2.