Lubricating oils are obtained by dehydrogenating hydrocarbon oils having a substantial content, e.g. 20-80 per cent of paraffin wax, separating the products by solvents into a fraction containing more than 14,5 parts by weight of hydrogen to 100 parts of carbon, and a fraction poorer in hydrogen, and subjecting the fraction richer in hydrogen, maybe mixed with hydrocarbon which is liquid at a temperature between 50 and 300 DEG C., to catalytic condensation or/and polymerization. The products may be used to improve inferior oils, and the fractions poorer in hydrogen may be hydrogenated and fractioned to produce motor fuels. Initial materials specified are brown coal tar oils, mineral oils, petrolatum or other refining or distillation residue of petroleum, petroleum jelly, crude paraffin wax, crude lubricating oils, or wax-containing products of the destructive hydrogenation of coals, tars, and mineral oils. The dehydrogenation may be effected by: (1) introducing substituents, e.g. chlorine or other halogen or sulphur, and removing hydrogen compounds thereof, e.g. in the case of halogens by heating to 200-400 DEG C. in presence of catalysts such as alumina, bauxite, zinc chloride, barium chloride, or titanium oxide; or (2) treating with oxidizing gases, e.g. air or oxygen, and splitting off water or water and carbon dioxide in presence of phosphorus pentoxide or caustic alkalis; or (3) cracking, preferably mildly, at 450-600 DEG C. in presence of catalysts such as metals of the 6th group or their oxides or compounds alone or mixed with each other or copper or other splitting catalysts, maybe with an addition of hydrogen. Solvents specified are liquid sulphur dioxide, aniline, liquid phenols, alcohols, or ketones. Condensation is effected at 20-150 DEG C. in presence of condensing agents, e.g. aluminium chloride, zinc chloride, iron chloride, boron fluoride, phosphorus oxychloride, activated aluminium, sodium, or zinc dust; bleaching earths may be present, or the products of condensation may be treated with bleaching earths. Added hydrocarbons which may be present are naphthalene, coal tar fractions, e.g. crude benzene, aromatic middle oil, and anthracene oil, aromatic oils obtained by the destructive hydrogenation of coals or their tars or by condensation at elevated temperatures of cracking gases or other olefines, brown coal tars, mineral oils, distillation, extraction, or destructive hydrogenation products thereof, and liquid olefines obtained by cracking solid paraffin waxes. In examples (1) 100 lb. of petrolatum is cracked several times at 490-530 DEG C., and the 72 lb. of oil boiling up to 300 DEG C. is treated with liquid sulphur dioxide; the 60 lb. undissolved is condensed at 30-110 DEG C. in presence of 3 lb. of aluminium chloride; there results 25 lb. of lubricating oil and 35 lb. of benzine and middle oil. (2) The 200-280 DEG C. fraction of a hydrogenated German crude oil is treated with chlorine until 18 per cent is absorbed; hydrogen chloride is split off by heating to 350 DEG C. in presence of bauxite, and the product treated with liquid sulphur dioxide; 100 lb. of the insoluble oil is condensed at 30-100 DEG C. in presence of 7 lb. of aluminium chloride; 30 lb. of lubricating oil, and unchanged oil are obtained.ALSO:Lubricating oils are obtained by dehydrogenating hydrocarbon oils having a substantial content, e.g. 20-80 per cent of paraffin wax, separating the products by solvents into a fraction containing more than 14,5 parts by weight of hydrogen to 100 parts of carbon, and a fraction poorer in hydrogen, and subjecting the fraction richer in hydrogen, may be mixed with hydrocarbon which is liquid at a temperature between 50 DEG and 300 DEG C., to catalytic condensation or/and polymerization. The products maybe used to improve inferior oils, and the fractions poorer in hydrogen may be hydrogenated and fractioned to produce motor fuels. Initial materials specified are brown coal tar oils, mineral oils, petrolatum or other refining or distillation residue of petroleum, petroleum jelly, crude paraffin wax, crude lubricating oils, or wax-containing products of the destructive hydrogenation of coals, tars, and mineral oils. The dehydrogenation may be effected by (1) introducing substituents, e.g. chlorine or other halogen or sulphur, and removing hydrogen compounds thereof, e.g. in the case of halogens by heating to 200-400 DEG C. in presence of catalysts such as alumina, bauxite, zinc chloride, barium chloride, or titanium oxide; or (2) treating with oxidizing gases, e.g. air or oxygen, and splitting off water or water and carbon dioxide in presence of phosphorus pentoxide or caustic alkalis; or (3) cracking, preferably mildly, at 450-600 DEG C. in presence of catalysts such as metals of the 6th group or their oxides or compounds alone or mixed with each other or copper or other splitting catalysts, maybe with an addition of hydrogen. Solvents specified are liquid sulphur dioxide, aniline, liquid phenols, alcohols, or k ketones. Condensation is effected p at 20-150 DEG C. in presence of condensing agents, e.g. aluminium chloride, zinc chloride, iron chloride, boron fluoride, phosphorus oxychloride, activated aluminium, sodium, or zinc dust; bleaching earths maybe present, or the products of condensation may be treated with bleaching earths. Added hydrocarbons which may be present are naphthalene, coal tar fractions, e.g. crude benzene, aromatic middle oil, and anthracene oil, aromatic oils obtained by the destructive hydrogenation of coals or their tars or by condensation at elevated temperatures of cracking gases or other olefines, brown coal tars, mineral oils, distillation, extraction, or destructive hydrogenation products thereof, and liquid olefines obtained by cracking solid paraffin waxes. In examples (1) 100 lbs. of petrolatum is cracked several times at 490-530 DEG C., and the 72 lbs. of oil boiling up to 300 DEG C. is treated with liquid sulphur dioxide; the 60 lbs. undissolved is condensed at 30-110 DEG C. in presence of 3 lbs. of aluminium chloride; there results 25 lbs. of lubricating oil and 35 lbs. of benzine and middle oil. (2) The 200-280 DEG C. fraction of a hydrogenated German crude oil is treated with chlorine until 18 per cent is absorbed; hydrogen chloride is split off by heating to 350 DEG C. in presence of bauxite, and the product treated with liquid sulphur dioxide; 100 lbs. of the insoluble oil is condensed at 30-100 DEG C. in presence of 7 lbs. of aluminium chloride; 30 lbs. of lubricating oil, and unchanged oil are obtained.