Lubricating composition for lead and copper corrosion inhibition

1. A lubricating composition comprising:

(a) an oil of lubricating viscosity;

(b) an ashless thiocarbamate compound having an S-atom substituted with a C 6 to C 20 aliphatic hydrocarbon and a N-atom substituted with a C 6 to C 20 aliphatic or aromatic hydrocarbon in an amount from 0.1 wt % to 0.5 wt %; and

(c) a boron-containing compound that is the reaction product of boric acid and a C 8 to C 10 alcohol in an amount sufficient to provide 20 ppm to 300 ppm of boron to the lubricating composition.

2. The lubricating composition of claim 1 , wherein the ashless thiocarbamate compound is represented by the formula (2):

wherein R 1 is an aliphatic hydrocarbon group containing 6 to 20 carbon atoms; and

R 2 is a aliphatic or aromatic hydrocarbon group containing 6 to 20 carbon atoms.

3. The lubricating composition of claim 1 , wherein the ashless thiocarbamate compound having an optionally-substituted hydrocarbyl group on an S-atom and an optionally-substituted hydrocarbyl group on an N-atom is represented by the formula (4):

wherein

Y is >O, or >S, or >NH or >NR 5 ;

R 2 is a hydrocarbyl group containing 2 to 60 carbon atoms, or a heterocycle or substituted equivalents thereof, with the proviso that R 2 is free of a nitrogen-containing heterocycle;

R 3 is a hydrocarbylene group containing 1 to 16 carbon atoms, or a heterocycle or substituted equivalents thereof;

R 4 is a hydrocarbyl group containing 2 to 60 carbon atoms, or a heterocycle or substituted equivalents thereof; and

R 5 is a hydrocarbyl group containing 1 to 30 carbon atoms.

4. The lubricating composition of claim 1 , wherein one or more of the C 6 to C 20 aliphatic hydrocarbon group substituted on the S-atom and the C 6 to C 20 aliphatic hydrocarbon group substituted on N-atom are linear hydrocarbyl hydrocarbon groups.

5. The lubricating composition of claim 1 , wherein one or more of the of the C 6 to C 20 aliphatic hydrocarbon group substituted on the S-atom and the C 6 to C 20 aliphatic hydrocarbon group substituted on N-atom are selected from a linear hydrocarbon group and a branched hydrocarbon group.

6. The lubricating composition of claim 1 , wherein one or more of the of the C 6 to C 20 aliphatic hydrocarbon group substituted on the S-atom and the C 6 to C 20 aliphatic hydrocarbon group substituted on N-atom are cyclic hydrocarbon groups.

7. The lubricating composition of claim 1 , wherein or more of the of the C 6 to C 20 aliphatic hydrocarbon group substituted on the S-atom and the C 6 to C 20 aliphatic hydrocarbon group substituted on N-atom are selected from a cyclic hydrocarbyl group and a linear hydrocarbyl group.

8. The lubricating composition of claim 1 , wherein the lubricating composition is characterized as having (i) a sulfur content of 0.5 wt % or less, (ii) a phosphorus content of 0.1 wt % or less, and (iii) a sulfated ash content of 0.5 wt % to 1.5 wt % or less.

9. The lubricating composition of claim 1 , wherein the lubricating composition is characterized as having at least one of (i) a sulfur content of 0.2 wt % to 0.4 wt % or less, (ii) a phosphorus content of 0.08 wt % to 0.15 wt %, and (iii) a sulfated ash content of 0.5 wt % to 1.5 wt % or less.

10. The lubricating composition of claim 1 , wherein the lubricating composition is characterized as having a sulfated ash content of 0.5 wt % to 1.2 wt %.

11. The lubricating composition of claim 1 , further comprising at least one of an antiwear agent, a dispersant viscosity modifier, a friction modifier, a corrosion inhibitor (other than the ashless thiocarbamate compound of claim 1 ) a viscosity modifier, an antioxidant, an overbased detergent, or mixtures thereof.

12. The lubricating composition of claim 11 , wherein the friction modifier is selected from the group consisting of long chain fatty acid derivatives of amines, long chain fatty esters, long chain fatty epoxides; fatty imidazolines; amine salts of alkylphosphoric acids; fatty alkyl citrates, fatty alkyl tartrates; fatty alkyl tartrimides; and fatty alkyl tartramides.

13. The lubricating composition of claim 1 , wherein the composition is free of long chain fatty esters.

14. The lubricating composition of claim 1 , further comprising a dispersant viscosity modifier.

15. The lubricating composition of claim 1 , further comprising a phosphorus-containing antiwear agent.

16. The lubricating composition of claim 1 , further comprising an overbased detergent selected from the group consisting of phenates, sulfur containing phenates, sulfonates, salixarates, salicylates, and mixtures thereof.

17. The lubricating composition of claim 16 , wherein the overbased detergent is present at 1 wt % to 10 wt %.

18. The lubricating composition of claim 1 , further comprising a succinimide dispersant.

19. The lubricating composition of claim 18 , wherein the succinimide dispersant is present at 2.5 wt % to 6 wt %.

20. The lubricating composition of claim 1 , wherein the lubricating composition has a TBN in the range of 3 to 15 mg KOH/g.

21. A method of lubricating an internal combustion engine comprising supplying to the internal combustion engine a lubricating composition of claim 1 .

22. The method of claim 21 , wherein the internal combustion engine is lubricated with a lubricating composition of claim 1 , and wherein the engine has a steel surface on a cylinder bore, a cylinder block, or a piston ring.

23. A method of lubricating a heavy duty diesel internal combustion engine comprising supplying to the heavy duty diesel internal combustion engine a lubricating composition of claim 1 .

24. The lubricating composition of claim 1 , wherein the boron-containing compound is a borate ester.

25. The lubricating composition of claim 1 , wherein the boron-containing compound is a borated fatty acid ester of glycerol.