Lubricating oil composition containing a dispersing-varnish inhibiting combination of an oxazoline compound and an acyl nitrogen compound

A lubricating oil composition comprising a major amount of lubricating oil and a minor but dispersing amount of a dispersing and varnish inhibiting combination of:

• (a) one part by weight of an oil-soluble oxazoline reaction product having a number average molecular weight of from about 1,000 to about 3,300 obtained from the reaction of one molar proportion of a hydrocarbyl substituted C.sub.4 -C.sub.10 monounsaturated dicarboxylic acid material wherein said hydrocarbyl substituent contains at least 50 aliphatic carbon atoms, and from about 1.5 to about 2 molar proportions of a 2,2-disubstituted-2-amino-1-alkanol having 2 to 3 hydroxy groups and containing a total of 4 to 8 carbons and represented by the formula:
• ##STR11## wherein X is an alkyl, or hydroxy alkyl group, with at least one of the X substituents being a hydroxy alkyl group of the structure --(CH.sub.2).sub.n OH, wherein n is 1 to 3;
• and, (b) from 0.25 to 4 parts by weight of an oil-soluble acylated nitrogen compound having a number average molecular weight ranging from about 1,300 to 8,000 characterized by the presence within its structure of a substantially saturated hydrocarbon-substituted polar group selected from the class consisting of acyl, acylimidoyl, and acyloxy radicals wherein the substantially saturated hydrocarbon substituent contains at least about 50 aliphatic carbon atoms and a nitrogen-containing group characterized by a nitrogen atom attached directly to said polar radical.