Dispersant additives and additive concentrates and lubricating oil compositions containing same

A lubricant additive concentrate having a kinematic viscosity of from about 40 to about 300 cSt., as measured at 100° C., comprising a dispersant-detergent colloid complex in diluent oil, wherein said dispersant comprises a polybutenyl succinimide reaction product of a polyamine having, or having on average 4 to 8 nitrogen atoms per molecule and polybutenyl succinic anhydride (PIBSA) derived from polybutene having a number average molecular weight of from about 1300 to about 2500 daltons and a terminal vinylidene content of at least about 65%, and maleic and/or succinic anhydride, by an ene maleation process, and having a succinic anhydride (SA) functionality of greater than 1.7, and less than about 2.5;

• and said detergent colloid comprises overbased detergent having a total base number (TBN) of from about 370 to about 1000 mg KOH/g, derived from one or more surfactants selected from (i) sulfonate;
• (ii) phenate;
• and (iii) carboxylate surfactants;
• wherein the mass ratio of said dispersant to said detergent colloid in the concentrate is from about 1.4 to about 3.0;
• and said dispersant and detergent colloid together constitute at least 28 mass % to about 50 mass %, on an A.I. basis, of said concentrate.