Abstract: A composition is disclosed which comprises a lubricating oil and a refrigerant, wherein the lubricating oil comprises a polyalkyleneglycol derivative of the formula (I): RX(RaO)x(RbO)y(RcO)zRd, wherein: X?O or S, R is a C3 to C15 substituent comprising a heterocyclic ring, in which the heteroatom(s) in said ring is (are) oxygen and/or sulphur, Ra is a C2 alkylene group, Rb is a C3 alkylene group, Rc is a C4 alkylene group, Rd is the same as R, or is H, a C1-C20 alkyl or a C1-C20 acyl, x, y, z are each independently 0 or an integer of 100 or less, and x+y+z=4 to 100, but excluding compositions where the refrigerant is halogen-free and R contains a carbonate group. The use of borate esters as dehydrogenating agents in conjunction with the above lubricating oils is also disclosed.