Lubricating composition containing an antiwear agent

A method of reducing lead corrosion of lead or lead alloy components in an internal combustion engine, said method comprising supplying to the internal combustion engine a lubricating composition comprising 46 to 97.9 wt %, of an oil of lubricating viscosity, from 0.1 to 0.5 wt % of a nitrile compound of formula (2):

• wherein, T is —C≡N;
• R5 is hydrogen;
• V is a hydrocarbyl group containing 4 to 20 carbon atoms;
• Z is —S—;
• A is hydrogen;
• and E is a hydrocarbyl group containing 4 to 20 carbon atoms, and from 0.5 wt % to 1.5 wt % of zinc dialkyldithiophosphate,
• 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, and;
• thereby reducing lead corrosion in said lead or lead alloy components.