Synthetic rubbers, e.g. isobutylene-diolefin and butadiene-styrene copolymers are plasticized with ethers obtained from the mixed alcohols produced by the " oxo " process (see Group IV (b)), said ethers having the formula R-O-R1 wherein R and R1 represent hydrocarbon radicals having at least 8, preferably 10 to 20, carbon atoms, and wherein either or both R and R1 represent branched-chain hydrocarbon radicals.ALSO:The invention comprises ethers of the general formula R-O-R1, wherein R and R1 represent hydrocarbon radicals having at least 8 carbon atoms, preferably 10 to 20 carbon atoms, and wherein either or both of the symbols R and R1 represent branched-chain hydrocarbon radicals, characterized in that said ethers are obtained from the mixed alcohols produced by the oxo process. The preferred ethers are those having pour points below 20 DEG F. and flash points above 300 DEG F. Suitable oxo alcohols are obtained by subjecting dimers, trimers, tetramers or higher polymers or copolymers of propylene, butylene or isobutylene to the oxo process and hydrogenating the products. The oxo ethers may be prepared by heating the oxo alcohols with sulphuric acid or p-toluene-sulphonic acid. The ethers may be used as lubricants, in lubricating compositions (see Group III), and as plasticizers for synthetic rubbers (see Group IV (a)). Examples describe the preparation of ethers by heating C13 or C16 oxo alcohols with sulphuric acid or p-toluenesulphonic acid.ALSO:Lubricating compositions comprise ethers having the general formula ROR1, wherein R and R1 represent hydrocarbon radicals having at least 8, preferably 10 to 20, carbon atoms and wherein either or both R and R1 represent branched-chain radicals, characterized in that said ethers are obtained from the mixed alcohols produced by the oxo process (see Group IV(b)), together with other lubricants, such as mineral oils, esters, formals, mercaptals, polyethers and oxidized mineral oils, or together with from 2-30 per cent by weight of an extreme pressure agent containing sulphur and/or phosphorus and/or halogen, e.g. tri-cresyl phosphate. The ethers may also be blended with viscosity index improvers, anti-foamants, pour depressants, and anti-oxidants. Lubricating greases are obtained by incorporating into the ethers a grease thickener, preferably an alkali or alkaline earth metal soap of a C10-C30 fatty acid or a complex metal soap of a C10-C30 fatty acid and a C1-C5 carboxylic acid such as acetic, furoic, acrylic, or crotonic acid. In examples, lubricating greases are obtained from a C13 oxo ether together with a complex lithium soap of co-neutralized Hydrofol Acids 54 and acetic or crotonic acid, and (1) phenyl-a -naphthylamine, (2) phenothiazine or (3) C8 oxo phosphate and phenyl-a -naphthyamine.