The thermal degradation of blends of different percentages of low-density polyethylene (LDPE) in vacuum gas oil (VGO) has been carried out in a fluidized-bed reactor. A wide range of percentages of the polymer has been selected for the study, including 0, 5, 25, 75, and 100% LDPE by weight. The strategy of mixing plastics with a solvent to be degraded avoids the possible heat-transfer limitations and other problems present in the cracking of solid plastics. A temperature of 500 degrees C has been selected as the degradation temperature in order to simulate industrial conditions of a refinery and, in this way, to evaluate the applicability of the products generated. The results show a significant increase of the volatile yields by increasing the amount of LDPE present in the blend, dry gas, and liquefied petroleum gas, increasing with the percentage of polymer mixed with VGO. Condensable products exhibit a decrease of their yield with this variable. The influence of the temperature at the exit of the reactor is also evaluated in the present work. Significant differences have been observed in the product distribution as a function of this parameter, showing the importance of the temperature profile on the results obtained in this type of reactor. The methodology shown in the present work could suggest the possibility of using a refinery stream of secondary interest (such as the VGO employed) and, simultaneously, recycling plastics, reducing the environmental problems they cause.