A process for the production of hydrocarbon-containing oils, in which a starting material containing a sugar and/or a sugar derivative is thermally cleaved, including a reaction step in which the starting material is brought into contact with a contact oil which has an initial boiling point of at least about 200.degree. C. at a pressure of about 1013 mbar with formation of a reaction phase at a reaction temperature in the range of from about 200 to about 600.degree. C. and a pressure in the range of from about 0.1 to about 50 bar. The process also includes a processing step in which the reaction phase is separated into a low-boiling fraction and a high-boiling fraction. At least a portion of the high-boiling fraction is recirculated into the reaction step as contact oil. The invention also relates to a system for this process which is equipped with an oilification module.