Disclosed is a method of lubrication including a step of lubricating a machine with a lubricating composition, the lubricating composition including 20-100% ionic liquid or of a mixture of several ionic liquids. The ionic liquid or the mixture is selected from at least: an anion A.sup.− chosen from sulfonylimides, the substituent(s) of which is (are) independently chosen from a fluoroalkyl, fluoroether, perfluorinated alkyl or perfluoroether group; and a cation C.sup.+ including a nitrogen-containing heterocycle or a quaternary ammonium, the substituent(s) of which is (are) independently chosen from: a hydrogen atom or alkyl, alkoxy, fluorinated alkyl, perfluorinated alkyl, alkylsilane, alkyl alcohol, vinyl, alkyl allyl, ether or polyether groups having a linear or branched chain having 1-3 carbon atoms. The deposition start temperature in thin film of the ionic liquid or of the mixture of ionic liquids is at least equal to 330° C. The lubricating composition reduces deposits formed in the machine.

Disclosed is a method of lubrication including a step of lubricating a machine with a lubricating composition, the lubricating composition including 20-100% ionic liquid or of a mixture of several ionic liquids. The ionic liquid or the mixture is selected from at least: an anion A.sup.− chosen from sulfonylimides, the substituent(s) of which is (are) independently chosen from a fluoroalkyl, fluoroether, perfluorinated alkyl or perfluoroether group; and a cation C.sup.+ including a nitrogen-containing heterocycle or a quaternary ammonium, the substituent(s) of which is (are) independently chosen from: a hydrogen atom or alkyl, alkoxy, fluorinated alkyl, perfluorinated alkyl, alkylsilane, alkyl alcohol, vinyl, alkyl allyl, ether or polyether groups having a linear or branched chain having 1-3 carbon atoms. The deposition start temperature in thin film of the ionic liquid or of the mixture of ionic liquids is at least equal to 330° C. The lubricating composition reduces deposits formed in the machine.

A lubricant including an ionic liquid, which includes a conjugate acid (B.sup.+) and a conjugate base (X.sup.), and is protic, wherein the ionic liquid is represented by the following general formula (1): ##STR00001##
where R.sup.1 and R.sup.2 each represent a hydrogen atom or R.sup.1 and R.sup.2 form a benzene ring together with carbon atoms to which R.sup.1 and R.sup.2 are bonded, and R.sup.3 represents a straight-chain hydrocarbon group having 10 or more carbon atoms in the general formula (1).

A lubricant including an ionic liquid, which includes a conjugate acid (B.sup.+) and a conjugate base (X.sup.), and is protic, wherein the ionic liquid is represented by the following general formula (1): ##STR00001##
where R.sup.1 and R.sup.2 each represent a hydrogen atom or R.sup.1 and R.sup.2 form a benzene ring together with carbon atoms to which R.sup.1 and R.sup.2 are bonded, and R.sup.3 represents a straight-chain hydrocarbon group having 10 or more carbon atoms in the general formula (1).

A lubricant including an ionic liquid, which includes a conjugate acid (B.sup.+) and a conjugate base (X.sup.), and is protic, wherein the ionic liquid is represented by the following general formula (1):

##STR00001##

where R.sup.1 and R.sup.2 each represent a hydrogen atom or R.sup.1 and R.sup.2 form a benzene ring together with carbon atoms to which R.sup.1 and R.sup.2 are bonded, and R.sup.3 represents a straight-chain hydrocarbon group having 10 or more carbon atoms in the general formula (1).

A lubricant including an ionic liquid, which includes a conjugate acid (B.sup.+) and a conjugate base (X.sup.), and is protic, wherein the ionic liquid is represented by the following general formula (1):

##STR00001##

where R.sup.1 and R.sup.2 each represent a hydrogen atom or R.sup.1 and R.sup.2 form a benzene ring together with carbon atoms to which R.sup.1 and R.sup.2 are bonded, and R.sup.3 represents a straight-chain hydrocarbon group having 10 or more carbon atoms in the general formula (1).