A polyalkylene glycol having an end-group of the general formula:

##STR00001## in which each R.sup.2 independently represents a hydroxyl, alkyl, alkenyl, aryl, heteroaryl, benzyl, or polyalkylene glycol group, and each R.sup.3 independently represents a hydroxyl, alkyl, alkenyl, aryl, heteroaryl, benzyl, or polyalkylene glycol group; m is 0, 1, 2, 3, 4, 5 or 6; and n is 0, 1, 2 or 3. A lubricating oil composition comprising this polyalkylene glycol. A refrigerant composition comprising this polyalkylene glycol. A method of lubricating moving parts of an industrial or automotive system comprising applying a composition to the parts, wherein the composition comprises this polyalkylene glycol.

A capped oil soluble polyalkylene glycol has the following structure: R.sup.1O-(AO).sub.nR.sup.2 where: R.sup.1 is a linear or branched alkyl or aryl with one to 18 carbon atoms; AO refers to residuals of monomers selected from 1,2-butylene oxide and 1,2-propylene oxide selected so that at least 50 weight-percent of the (AO).sub.n component is 1,2-butylene oxide residuals; n is selected to provide a kinematic viscosity at 100 degrees Celsius of less than 5 centiStokes for the non-capped polyalkylene glycol; and R.sup.2 is a linear or branched alkyl or aryl having from 1-8 carbon atoms and wherein the capped oil soluble polyalkylene glycol is characterized by having a kinematic viscosity of less than 4.5 centiStokes at 100 degrees Celsius and a viscosity index of greater than 150.

A capped oil soluble polyalkylene glycol has the following structure: R.sup.1O-(AO).sub.nR.sup.2 where: R.sup.1 is a linear or branched alkyl or aryl with one to 18 carbon atoms; AO refers to residuals of monomers selected from 1,2-butylene oxide and 1,2-propylene oxide selected so that at least 50 weight-percent of the (AO).sub.n component is 1,2-butylene oxide residuals; n is selected to provide a kinematic viscosity at 100 degrees Celsius of less than 5 centiStokes for the non-capped polyalkylene glycol; and R.sup.2 is a linear or branched alkyl or aryl having from 1-8 carbon atoms and wherein the capped oil soluble polyalkylene glycol is characterized by having a kinematic viscosity of less than 4.5 centiStokes at 100 degrees Celsius and a viscosity index of greater than 150.

[Problem]

Provided is an operating oil for shock absorber in which influences against rubber materials are controlled.

[Solution]

An operating oil coming into contact with a rubber material, the operating oil containing a polyalkylene glycol and at least one base oil selected from a fatty acid diester, a poly-alfa-olefin, and a lubricating oil classified as GIII in American Petroleum Institute (API).

[Effect]

According to the operating oil, in view of the fact that swelling properties of a rubber material, such as a seal material, etc., are reduced, conventionally used rubber materials can be used without being changed.

[Problem]

Provided is an operating oil for shock absorber in which influences against rubber materials are controlled.

[Solution]

An operating oil coming into contact with a rubber material, the operating oil containing a polyalkylene glycol and at least one base oil selected from a fatty acid diester, a poly-alfa-olefin, and a lubricating oil classified as GIII in American Petroleum Institute (API).

[Effect]

According to the operating oil, in view of the fact that swelling properties of a rubber material, such as a seal material, etc., are reduced, conventionally used rubber materials can be used without being changed.

The refrigerating machine oil according to the present invention comprises a polyalkylene glycol represented by the following formula (1):

R.sup.1(OR.sup.3).sub.nOR.sup.2(1) [R.sup.1 and R.sup.2 may be the same or different from each other and each represent a hydrogen atom, an alkyl group having from 1 to 5 carbon atoms, or an acyl group having from 2 to 5 carbon atoms, R.sup.3 represents an alkylene group having from 2 to 4 carbon atoms, n represents an integer such that a number average molecular weight of the polyalkylene glycol represented by the formula (1) is from 1000 to 2500] the polyalkylene glycol having a ratio of the weight average molecular weight Mw to the number average molecular weight Mn, Mw/Mn, of from 1.00 to 1.15, the refrigerating machine oil being used with a mildly flammable hydrofluorocarbon refrigerant.

A fluid contains a base oil consisting of an alcohol-initiated polyalkylene glycol where polyalkylene glycol component is selected from a homopolymer of 1,2-butylene oxide and copolymer of 1,2-butylene oxide and propylene oxide; a glycerol-initiated unsaturated ester that is free of tertiary carbon atoms and quaternary carbon atoms; and an antioxidant.

A fluid contains a base oil consisting of an alcohol-initiated polyalkylene glycol where polyalkylene glycol component is selected from a homopolymer of 1,2-butylene oxide and copolymer of 1,2-butylene oxide and propylene oxide; a glycerol-initiated unsaturated ester that is free of tertiary carbon atoms and quaternary carbon atoms; and an antioxidant.

Disclosed is the use of a lubricating composition including at least one base oil and at least one polyalkylene glycol (PAG) produced by polymerisation or copolymerisation of alkylene oxides including between 3 and 8 carbon atoms, at least one of which being a butylene oxide, for preventing or reducing pre-ignition in an engine, preferably in a vehicle engine.

Disclosed is the use of a lubricating composition including at least one base oil and at least one polyalkylene glycol (PAG) produced by polymerisation or copolymerisation of alkylene oxides including between 3 and 8 carbon atoms, at least one of which being a butylene oxide, for preventing or reducing pre-ignition in an engine, preferably in a vehicle engine.