Lubricating composition containing an antiwear agent

1. A lubricating composition comprising

(a) an oil of lubricating viscosity,

(b) 0.5 wt % to 1.0 wt % of a phosphite having at least one hydrocarbyl group that has 4 or more carbon atoms, wherein the phosphite having at least one hydrocarbyl group with 4 or more is represented by the formula:

wherein at least one of R 3 , R 4 and R 5 is a hydrocarbyl group containing from at least 4 carbon atoms and the other may be hydrogen or a hydrocarbyl group, and wherein the phosphite has at least one hydrocarbyl group with 16 to 18 carbon atoms, and

(c) 0.1 wt % to 0.5 wt % of a compound derived from an ester of a hydroxy-carboxylic acid having linear or branched alkyl groups of 1 to 20 carbon atoms and selected from the group consisting of malic acid, citric acid, or mixtures thereof; and

(d) an overbased magnesium sulphonate detergent having a TBN of from 250 to 600 present in an amount from about 0.2 wt % to about 8 wt %;

wherein the lubricating composition is characterised as having (i) a sulphur content of 0.5 wt % or less, (ii) a phosphorus content of 0.1 wt % or less, and (iii) a sulphated ash content of 1.5 wt % or less.

2. The lubricating composition of claim 1 , wherein n and m both equal 2.

3. The lubricating composition of claim 1 , wherein both R 3 and R 4 are hydrocarbyl groups.

4. The lubricating composition of claim 1 further comprising a zinc dialkyldithiophosphate, or mixtures thereof, wherein the zinc dialkyldithiophosphate is present at 0.75 wt % to 1.5 wt % of the lubricating composition.

5. The lubricating composition of claim 1 further comprising at least one of an antiwear agent, a dispersant viscosity modifier, a friction modifier, a viscosity modifier, an antioxidant, an overbased detergent, or mixtures thereof.

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

7. The method of claim 6 , wherein the internal combustion engine has surfaces of an aluminium alloy, or aluminium composite.

8. The method of claim 7 , wherein the aluminium alloy is a eutectic or hyper-eutectic aluminium alloy.

9. The method of claim 8 , wherein the aluminium alloy is derived from an aluminium silicate.

10. The method of claim 6 , wherein the internal combustion engine has surfaces of steel.

11. The method of claim 1 , wherein the compound is derived from malic acid.

12. The method of claim 1 , wherein the compound is derived from citric acid.

13. The method of claim 1 , wherein the lubricating composition is free of zinc dialkyldithiophosphate.