Complex esters having the general formula R2OOC-R1-COO-R3-OOC-R11 -COOR12 in which the various Rs have the meanings herein after defined, are prepared by reaction under esterification conditions of stoichiometric proportions of appropriate monohydric alcohols, glycols and dibasic acids or their esterifying equivalents, the various Rs being so selected that the molecular weight of the complex ester is at least 300 and the complex ester contains at least two "hetero" atoms in the molecule and possesses an A.S.T.M. pour point not higher than -10 DEG F. In the above formula, R1 and R11 represent the same or different C4 to C8 straight chain alkylene groups; R3 is a polyglycol or polythioglycol radical containing from 5 to 80 carbon plus "hetero" atoms ("hetero" meaning oxygen or sulphur) with a maximum of two sulphur atoms; R2 and R12 which may be the same or different represent (a) saturated straight chain C1-C5 aliphatic hydrocarbon radicals; (b) saturated branched chain C3-C20 aliphatic hydrocarbon radicals, or (c) a series of saturated aliphatic hydrocarbons interlinked by ether oxygen and/or thio ether sulphur, the total number of carbon and hetero atoms in the radical being from 4 to 20 and the total number of hetero atoms in the radical not exceeding 5; there must be at least 2 carbon atoms between the carboxyl groups of the formula and the first hetero atom and a chain of at least 2 carbon atoms between any pair of adjacent hetero atoms. The complex esters may be prepared by reacting together equimolar proportions of the alcohol and dibasic acid to form the half-ester of the acid and then reacting two molar proportions of the half-ester with one molar proportion of the glycol. Suitable dibasic acids are adipic, pimelic, suberic, azelaic and sebacic acids; typical monohydric alcohols are methyl, ethyl, n-butyl and 2-ethyl hexyl alcohols, the mono n-butyl, mono-2-ethylbutyl and mono-2-ethylhexyl ethers of ethylene glycol and di-ethylene glycol, ethylene glycol mono-tert. octyl ether, propylene glycol mono-n-butyl ether, the mono-methyl, ethyl and n-butyl ethers of dipropylene and tripropylene glycols, the mono-isopropyl ethers of propylene, dipropylene and tripropylene glycols, propylene glycol mono butyl, tert. octyl and n-dodecyl thioethers, b - n - butylmercaptoethanol, b -tert. octyl mercapto ethanol, b -n-dodecyl-mercaptoethanol, n-butyl mercapto tert.-octylmercapto and n-dodecyl-ethoxyethanols, n-butylmercapto, tert. - octyl mercapto - and n-dodecyl-mercapto - propoxypropanols, and "oxo" alcohols from such olefines as di-isobutylene and C7 olefines. The glycols include polyethylene glycols having the general formula HO(CH2CH2O)nCH2CH2OH where n is 1 to 26, polypropylene glycols having the general formula <FORM:0680438/IV (a)/1> where R or R1 is a methyl group and the other is hydrogen and n is 1 to 18, thiodiglycol, 1,2-bis - (2 - hydroxyethylmercapto) ethane and bis-2-(2-hydroxyethoxy) ethyl sulphide. The complex esters may be used as lubricants with or without the usual additives, or with a mineral lubricating oil (see Group III). Examples are given of the production of complex esters using as the components, adipic acid, n-butyl alcohol and triethylene glycol; adipic acid, ethylene glycol mono ethyl ether and thiodiglycol; adipic acid, dipropylene glycol monoisopropyl ether and tetraethylene glycol; adipic acid, C10 "oxo" alcohol and tetraethylene glycol; thiodipropionic acid, n-butyl alcohol and trimethylene glycol. Specification 666,697, [Group IV (b)], is referred to in a disclaimer. The Specification as open to inspection under Sect. 91 relates to the production of esters of the above general formula wherein, however, R and R1 may be straight or branched chain aliphatic saturated hydrocarbon radicals containing up to 30 carbon atoms or a series of aliphatic hydrocarbon radicals interlinked by oxygen and/or sulphur, the total number of carbon and hetero atoms in each radical being from 3-40 with a maximum of 2 sulphur atoms, but see below, R2 and R12 are (a) aliphatic hydrocarbon radicals having 1-5 carbon atoms; (b) branched chain hydrocarbon radicals having 3-20 carbon atoms, or (c) a series of aliphatic hydrocarbon radicals interlinked with oxygen and/or sulphur, the total number of carbon and hetero atoms in each radical being 4-20 with a maximum of 5 hetero atoms. R3 is (a) an aliphatic hydrocarbon radical aving 2-20 carbon atoms, or (b) a series of aliphatic hydrocarbon radicals interlinked with oxygen or sulphur, the total number of carbon and hetero atoms being 5-80 with a maximum of 2 sulphur atoms. Additional examples of esters are those derived as above from adipic acid, n-butyl alcohol and trimethylene glycol; adipic or sebacic acid, C8 "oxo" alcohol and tri- or tetraethylene glycol; sebacic acid, 2-ethylhexanol and tetra ethylene glycol; C14-C18 alkenyl succinic acid, methyl alcohol and triethylene glycol; oxalic acid, C8 "oxo" alcohol and tetraethylene glycol. This subject-matter does not appear in the Specification as accepted.ALSO:Complex esters having the general formula R2OOC-R1-COO-R3-OOC-R11 -COOR12, in which the various R's have the meanings hereinafter defined, are prepared by reaction under esterification conditions of stoichiometric proportions of appropriate monohydric alcohols, glycols and dibasic acids or their esterifying equivalents, the various R's being so selected that the molecular weight of the complex ester is at least 300 and the complex ester contains at least two "hetero" atoms in the molecule and possesses an A.S.T.M. pour-point not higher than -10 DEG F. In the above formula, R1 and R11 represent the same or different C4 to C8 straight-chain alkylene groups; R3 is a polyglycol or polythioglycol radical containing from 5 to 80 carbon plus "hetero" atoms ("hetero" meaning oxygen or sulphur) with a maximum of two sulphur atoms; R2 and R12 which may be the same or different represent (a) saturated straight-chain C1-C5 aliphatic hydrocarbon radicals; (b) saturated branched-chain C3-C20 aliphatic hydrocarbon radicals; or (c) a series of saturated aliphatic hydrocarbons interlinked by ether oxygen and/or thio-ether sulphur, the total number of carbon and hetero atoms in the radical being from 4 to 20 and the total number of hetero atoms in the radical not exceeding 5; there must be at least 2 carbon atoms between the carboxyl groups of the formula and the first hetero atom and a chain of at least 2 carbon atoms between any pair of adjacent hetero atoms. The complex esters may be prepared by reacting together equimolar proportions of the alcohol and dibasic acid to form the half-ester of the acid and then reacting two molar proportions of the half-ester with one molar proportion of the glycol. Suitable dibasic acids are adipic, pimelic, suberic, azelaic and sebacic acids; typical monohydric alcohols are methyl, ethyl, n-butyl and 2-ethyl hexyl alcohols, the mono-n-butyl, mono-2-ethylbutyl and mono-2-ethylhexyl ethers of ethylene glycol and diethylene glycol, ethylene glycol mono-tert.-octyl ether, propylene glycol mono-n-butyl ether, the mono-methyl, ethyl and n-butyl ethers of dipropylene and tripropylene glycols, the mono isopropyl ethers of propylene, dipropylene and tripropylene glycols, propylene glycol mono-butyl-tert.-octyl- and n-dodecylthioethers, b -n-butyl-mercaptoethanol, b -tert.-octyl-mercaptoethanol, b -n-dodecyl-mercapto-ethanol, n-butyl-mercapto-tert.-octyl-mercapto- and n-dodecyl-ethoxyethanols, n-butyl-mercapto, tert.-octyl-mercapto- and n-dodecylmercapto-propoxypropanols, and "oxo" alcohols from such olefines as diisobutylene and C7 olefines. The glycols include polyethylene glycols having the general formula HO(CH2CH2O)nCH2CH2OH where n is 1 to 26, polypropylene glycols having the general formula <FORM:0680438/IV (b)/1> where R or R1 is a methyl group and the other is hydrogen and n is 1 to 18, thiodiglycol, 1,2-bis-(2-hydroxyethyl-mercapto) ethane and bis-2-(2-hydroxyethoxy) ethyl sulphide. The complex esters may be used as lubricants (see Group III). Examples are given of the production of complex esters using as the components, adipic acid, n butyl alcohol and triethylene glycol; adipic acid, ethylene glycol mono-ethyl ether and thiodiglycol; adipic acid, dipropylene glycol monoisopropyl ether and tetraethylene glycol; adipic acid, C10 "oxo" alcohol and tetraethylene glycol; thiodipropionic acid, n-butyl alcohol and trimethylene glycol; the method comprises half-esterification of the dibasic acid with the alcohol and then esterification of this half-ester with the glycol. Specification 666,697 is referred to in a disclaimer. The Specification as open to inspection under Sect. 91, relates to the production of esters of the above general formula wherein, however, R1 and R11 may be straight or branched chain aliphatic saturated hydrocarbon radicals containing up to 30 carbon atoms or a series of aliphatic hydrocarbon radicals interlinked by oxygen and/or sulphur, the total number of carbon and hetero atoms in each radical being from 3-40 with a maximum of 2 sulphur atoms, but see below, R2 and R12 are (a) aliphatic hydrocarbon radicals having 1-5 carbon atoms; (b) branched-chain hydrocarbon radicals having 3-20 carbon atoms; or (c) a series of aliphatic hydrocarbon radicals interlinked with oxygen and/or sulphur, the total number of carbon and hetero atoms in each radical being 4-20 with a maximum of 5 hetero atoms. R3 is (a) an aliphatic hydrocarbon radical having 2-20 carbon atoms or (b) a series of aliphatic hydrocarbon radicals interlinked with oxygen or sulphur, the total number of carbon and hetero atoms being 5-80 with a maximum of 2 sulphur atoms. Additional examples of esters are those derived as above from adipic acid, n-butyl alcohol and trimethylene glycol; adipic or sebacic acid, C8 "oxo" alcohol and tri- or tetra-ethylene glycol; sebacic aci