Provided is grease for a rolling bearing of an information recording and reproducing apparatus 1, containing a base oil, a thickener, and at least one kind of an antioxidant selected from an amine-based antioxidant (A) expressed by the General Formula (1), and a phenol-based antioxidant (B) expressed by the General Formula (2).

Provided is a fluorine-containing ether compound represented by the following formula. R.sup.1OR.sup.2CH.sub.2R.sup.3CH.sub.2R.sup.4OR.sup.5 (R.sup.3 represents a perfluoropolyether chain, R.sup.2 and R.sup.4 represent a divalent linking group having one or more polar groups, R.sup.1 and R.sup.5 represent Formula (2), Formula (3), or a hydrogen atom, and at least one of R.sup.1 or R.sup.5 is represented by Formula (2) or (3), in Formula (2), X.sup.1 represents an alkylene group having 1 to 30 carbon atoms, and Y and Z represent an aliphatic group having 1 to 30 carbon atoms, in Formula (3), X.sup.2 represents an alkylene group having 1 to 30 carbon atoms, and A and B represent an aliphatic group having 1 to 30 carbon atoms.)

##STR00001##

A working fluid filled in a refrigerant circulation system comprising a compressor, a condenser, an expansion mechanism, an evaporator, and an accumulator, the working fluid comprising: a refrigerant; and a refrigerating machine oil, wherein the refrigerant comprises a hydrocarbon refrigerant having 2 to 4 carbon atoms, the refrigerating machine oil has a mixed aniline point of 20 C. or higher and 50 C. or lower and a viscosity index of 110 or more, an amount of the refrigerant dissolved in the working fluid is 40% by mass or less under conditions of a temperature of 80 C. and an absolute pressure of 2.8 MPa, and the refrigerating machine oil has a kinematic viscosity at 10 C. of 200 mm.sup.2/s or more and 3000 mm.sup.2/s or less.

This fluorine-containing ether compound is a fluorine-containing ether compound represented by the following formula:

R.sup.1CH.sub.2R.sup.2(CH.sub.2OCH.sub.2CR.sup.3R.sup.4CH.sub.2OCH.sub.2R.sup.2).sub.zCH.sub.2R.sup.5

(z represents 1 or 2. R.sup.2 is a perfluoropolyether chain. R.sup.1 and R.sup.5 are terminal groups having 1 to 50 carbon atoms and having at least one polar group. R.sup.3 and R.sup.4 may be the same as or different from each other, and are organic groups which do not include a secondary hydroxy group and a tertiary hydroxy group, include one primary hydroxy group, and have 1 to 5 carbon atoms bonded to a tetrasubstituted carbon atom. The organic group may include an ether oxygen atom between the carbon atoms, and a bonding terminal to the tetrasubstituted carbon atom may be an ether oxygen atom.)

This fluorine-containing ether compound is a fluorine-containing ether compound represented by Formula (1). In Formula (1), X is Formula (2-1) to (2-5), and A is Formula (3-1) or (3-2). B is a perfluoropolyether chain. D has 2 to 4 polar groups, has an oxygen atom bonded to a methylene group adjacent to D, has 1 to 15 carbon atoms, and has 0 to 9 carbon atoms in a shortest distance between carbon atoms to which adjacent polar groups in D are bonded.

##STR00001##

A working medium contains (E)-1,3,3,3-tetrafluoropropene, (Z) 1-chloro-2,3,3,3-tetrafluoropropene, and 1,1,1,2-tetrafluoroethane, wherein, with respect to a total content of the (E)-1,3,3,3-tetrafluoropropene, the (Z) 1-chloro-2,3,3,3-tetrafluoropropene, and the 1,1,1,2-tetrafluoroethane, a content of the 1,1,1,2-tetrafluoroethane is 14.5% by mass or less, a content of the (Z) 1-chloro-2,3,3,3-tetrafluoropropene is 10.0% by mass or less, and a content of the (E)-1,3,3,3-tetrafluoropropene is 75.5% by mass or more.