Friction modifier compositions and their use

A lubricant composition which comprises a major amount of at least one oil of lubricating viscosity and an friction modifying amount of the combination of:

• a) a hydroxyalkyl aliphatic imidazoline in which the hydroxyalkyl group contains from 2 to about 4 carbon atoms, and in which the aliphatic group is an acyclic hydrocarbyl group containing from about 10 to about 25 carbon atoms;
• and
• b) a di(hydroxyalkyl) aliphatic tertiary amine in which the hydroxyalkyl groups, being the same or different, each contain from 2 to about 4 carbon atoms, and in which the aliphatic group is an acyclic hydrocarbyl group containing from about 10 to about 25 carbon atoms;
• said components a) and b) being present in a mol ratio in the range of about 0.005 to about 0.5 mol of a) per mol of b).

A method of maintaining a substantially constant static breakaway coefficient of friction between a pair of friction surfaces that are periodically frictionally engaged with each other which method comprises contacting said surfaces with a lubricant composition which comprises a major amount of at least one oil of lubricating viscosity and an friction modifying amount of the combination of:

• a) a hydroxyalkyl aliphatic imidazoline in which the hydroxyalkyl group contains from 2 to about 4 carbon atoms, and in which the aliphatic group is an acyclic hydrocarbyl group containing from about 10 to about 25 carbon atoms;
• and
• b) a di(hydroxyalkyl) aliphatic tertiary amine in which the hydroxyalkyl groups, being the same or different, each contain from 2 to about 4 carbon atoms, and in which the aliphatic group is an acyclic hydrocarbyl group containing from about 10 to about 25 carbon atoms;
• said components a) and b) being present in a mol ratio in the range of about 0.005 to about 0.5 mol of a) per mol of b).