An industrial oil composition contains a mineral or a synthetic oil as a base oil, and a neutral phosphite ester derivative represented by the following formula (B) and a 2,6-di-t-butylphenol derivative represented by the following formula (C) as antioxidants. In the formula (B), R.sup.b21 to R.sup.b24 each independently represent an aliphatic hydrocarbon group of 10 to 16 carbon atoms. In the formula (C), R.sup.c1 represents a straight-chain or a branched alkyl group of 1 to 12 carbon atoms.

##STR00001##

##STR00002##

A composition having a compound having the structure: ##STR00001##
wherein each R is an independently selected alkylphenol-free moiety that is a C.sub.1-20 alkyl, C.sub.2-22 alkenyl, C.sub.6-40 cycloalkyl, C.sub.7-40 cycloalkylene, C.sub.3-20 methoxy alkyl glycol ether, C.sub.3-20 alkyl glycol ether, or YOH moiety; wherein each Y is an independently selected alkylphenol-free moiety that is a C.sub.2-40 alkylene, C.sub.7-40 cycloalkylene, or C.sub.3-40 alkyl lactone moiety; wherein m is an integer ranging from 1 to 100; and wherein x is an integer ranging from 1 to 1000.

A composition having a compound having the structure:

##STR00001##

wherein each R is an independently selected alkylphenol-free moiety that is a C.sub.1-20 alkyl, C.sub.2-22 alkenyl, C.sub.6-40 cycloalkyl, C.sub.7-40 cycloalkylene, C.sub.3-20 methoxy alkyl glycol ether, C.sub.3-20 alkyl glycol ether, or YOH moiety; wherein each Y is an independently selected alkylphenol-free moiety that is a C.sub.2-40 alkylene, C.sub.7-40 cycloalkylene, or C.sub.3-40 alkyl lactone moiety; wherein m is an integer ranging from 1 to 100; and wherein x is an integer ranging from 1 to 1000.

The present disclosure relates to polysiloxanes, processes for preparing polysiloxanes, and hydraulic fluids comprising polysiloxanes. This disclosure also relates to hydraulic fluids comprising one or more polysiloxane compounds and diphosphonate compounds, and to the use of diphosphonate compounds in hydraulic fluids or as additives or components in various compositions, for example to provide fire retardant properties to a fluid or composition. This disclosure also relates to use of the compositions as hydraulic fluids, which may be used in various machines, vehicles and craft, including aircraft.