Quaternary ammonium salt containing compositions that provide balanced deposit control and wear performance without seal compatibility issues

1. A lubricant composition comprising

a major amount of an oil of lubricating viscosity;

(a) 0.3 to 5 percent by weight of a dispersant comprising a quaternary ammonium salt;

(b) 0.1 to 1.5 percent by weight of a zinc dialkyldithiophosphate;

(c) 0.5 to 1.0 percent by weight of a phosphorus-containing compound that is not a zinc dialkyldithiophosphate, comprising an alkyl phosphite;

(d) 0.5 to 1.0 percent by weight of a derivative of a hydroxyl-carboxylic acid and an alcohol; and

(e) 1.0 to 5 percent by weight of a non-quaternized dispersant comprising a succinimide dispersant prepared from PIB and a polyether polyamine;

wherein said percentages are based on the overall lubricant composition; and

wherein the weight ratio of component (c) to component (b) is at least 1.5:1.

2. The lubricant composition of claim 1 wherein component (a) comprises a quaternary ammonium salt comprising the reaction product of: (i) a compound comprising at least one tertiary amino group; and (ii) a quaternizing agent suitable for converting the tertiary amino group of compound (i) to a quaternary nitrogen group.

3. The lubricant composition of claim 1 wherein component (a) comprises the reaction product of (i) the reaction product of a polyhydroxy stearic acid and a polyamine where the resulting product has at least one tertiary amino group or at least one amino group that may be alkylated to a tertiary amino group; and (ii) a quaternizing agent suitable for converting the tertiary amino group of compound to a quaternary nitrogen group, and wherein component (a) may optionally further comprises a polyhydroxy stearic acid.

4. The lubricant composition of claim 1 wherein the zinc dialkyldithiophosphate where each of the alkyl groups are branched and contain from 4 to 12 carbon atoms.

5. The lubricant composition of claim 1 wherein component (d) comprises a compound derived from (i) an alcohol and (ii) a hydroxy-carboxylic acid represented by the formula:

wherein: a and b may be independently integers of 1 to 5; X 4 may be an aliphatic or alicyclic group, or an aliphatic or alicyclic group containing an oxygen atom in the carbon chain, or a substituted group of the foregoing types, said group containing up to 6 carbon atoms and having a+b available points of attachment; each Y 2 may be independently —O—, >NH, or >NR 6 or two Ys together representing the nitrogen of an imide structure R 4 —N<formed between two carbonyl groups; and each R 4 and R 6 may be independently hydrogen or a hydrocarbyl group, provided that at least one R 4 and R 6 group may be a hydrocarbyl group; each R 5 may be independently hydrogen, a hydrocarbyl group or an acyl group, further provided that at least one —OR 5 group is located on a carbon atom within X 4 that is α or β to at least one of the —C(O)—Y 2 —R 1 groups, and further provided that at least one R 5 is hydrogen.

6. The lubricant composition of claim 1 further comprising:

one or more antioxidants, one or more detergents, one or more friction modifiers other than component (d), one or more pour point depressants, one or more viscosity modifiers, one or more antifoam agents, one or more dispersants other than component (a), one or more antiwear agents other than components (b) and (c), or any combination thereof.

7. The lubricant composition of claim 1 wherein each of the alkyl groups of the zinc-dialkyldithiophosphate are branched and contain from 3 to 12 carbon atoms;

wherein component (d) comprises a compound derived from (i) an alcohol and (ii) a hydroxy-carboxylic acid represented by the formula:

wherein: a and b may be independently integers of 1 to 5; X 4 may be an aliphatic or alicyclic group, or an aliphatic or alicyclic group containing an oxygen atom in the carbon chain, or a substituted group of the foregoing types, said group containing up to 6 carbon atoms and having a+b available points of attachment; each Y 2 may be independently —O—, >NH, or >NR 6 or two Ys together representing the nitrogen of amine an imide structure R 4 —N<formed between two carbonyl groups; and each R 4 and R 6 may be independently hydrogen or a hydrocarbyl group, provided that at least one R 4 and R 6 group may be a hydrocarbyl group; each R 5 may be independently hydrogen, a hydrocarbyl group or an acyl group, further provided that at least one —OR 5 group is located on a carbon atom within X 4 that is α or β to at least one of the —C(O)—Y 2 —R 1 groups, and further provided that at least on R 5 is hydrogen.

8. A method of lubricating an internal combustion engine comprising the step of supplying to an internal combustion engine the lubricant composition of claim 1 .

9. A method of improving the overall performance of a lubricant composition balanced across the areas of deposit control, seal compatibility, and antiwear,

wherein said method comprises the step of adding to said lubricant the additive composition of claim 1 .