The present invention relates to a method for degrading synthetic polymers, in particular polyolefines, comprising the following steps a) the synthetic polymers, in particular dried, synthetic polymers, are melted in at least one extruder (E), b) the polymer melt is purified by guiding said polymer melt through at least one melt filter (SF), c) the purified polymer melt is transferred into at least one first reactor (R1), said purified polymer melt in the at least one first reactor (R1) is guided from a lower region into an upper region of the reactor (R1) by heating to temperatures of between 300 and 370° C, preferably 330° C to 360° C, in particular 350° C, the polymers in the at least one first reactor (R1) are cleaved into oligomers, d) the oligomer mixture formed in the at least one first reactor (R1) is transferred into at least one second reactor (R2), the oligomer mixture in the at least second reactor (R2) is guided from a lower region into an upper region of the reactor (R2) by heating to a temperature of between 380 to 450° C, preferably 400° C to 430° C, in particular 410° C, the oligomers in the at least one second reactor (R2) being degraded into short-chained hydrocarbons, in the presence of at least one clay mineral as a depolymerisation catalyst, e) the short-chained hydrocarbons formed in the at least one second reactor (R2) are discharged into at least one precondenser (VK), the short-chained hydrocarbons emerging from the at least one second reactor (R2) are cooled in the at least one precondenser (VK); and f) the short-chained hydrocarbons cooled in the at least one precondener (VK) are guided into at least one main condenser (HK), the short-chained hydrocarbons emerging from the at least one precondenser (VK) are liquefied in the at least one main condenser (HK). The invention also relates to a system for carrying out said method and to the product oil produced according to said method.