Lubricating oil compositions containing specified end-capped polyethers

A polyether having the formulaRX[(CxH2xO)n(CyH2yO)pZ]m(I)wherein: R is either an alkyl or alkyl phenyl group having from 7 to 30 carbon atoms, X is selected from O, S or N; x is an integer from 2 to 4; y is an integer from 6 to 30; Z is a hydrocarbyl group containing from 1 to 30 carbon atoms; m is 1 when X is O or S or m is 2 when X is N; n and p are such that the polyether contains between 1 and 40% by weight of (CyH2yO) units and between 40 and 80% by weight of (CxH2xO) units; and the molecular weight of the polyether is between 500 and 3,500. Lubricating oil compositions comprising such polyethers are disclosed. A method of preparing the polyethers is disclosed and comprises preparing a H-capped polyether, preparing an alkali-metal salt thereof and reacting said salt with an alkylating agent.