Lubricating oil additives

A lubricating oil composition comprising at least 50 percent by mass, based on the mass of the composition, of an oil of lubricating viscosity and 0.01 to 25 percent by mass, based on the mass of the composition, of a polymer comprising units (a) and one or both units (b) and (c):

• —N(COR1)(CH2)x— (a)
• —NH(CH2)y— (b)
• —N(CH2CH2-k(CH3)kCOOR2)(CH2)z (c)
• wherein the total number (n) of units (a), (b) and (c) is an integer between 4 and 500;
• wherein x, y and z are independently 2 or 3;
• wherein k is zero or 1;
• wherein the polymer carries an inorganic or organic nucleophilic polymerisation terminating group (t), and an initiator group (i) connected to the N atom of a unit (a), (b) or (c), the initiator group (i) being effective to initiate the polymerisation of linear, branched or cyclic hydrocarbyl moieties;
• wherein R1 comprises:
• i) a single linear, branched or cyclic hydrocarbyl group having 12 to 50 carbon atoms;
• ii) a mixture of linear, branched or cyclic hydrocarbyl groups having 1 to 50 carbon atoms, where some or all of the hydrocarbyl groups have 12 to 50 carbon atoms;
• or
• iii) at least one macro-monomeric hydrocarbyl group with more than 50 carbon atoms;
• and
• wherein R2 comprises a substituted or unsubstituted hydrocarbyl group having 1 to 30 carbon atoms, which group may be, linear or branched or cyclic, saturated or unsaturated, or aromatic.