In this UM 191 study, microwave pyrolysis using a reactor bed of particulate-carbon was performed on waste oil in the additional presence of different amounts of metallic-char produced previously from the pyrolysis process as the catalyst in order to understand the influence of the chemical nature and amount of the metallic-char on the yield of pyrolysis products and with an emphasis on the chemical composition of the oil and gaseous products. The metallic-char catalyst was pre-treated by calcination and characterized by different analytical methods before and after being subjected to pyrolysis. In addition, a study was performed to examine the heating characteristics of the mixture of waste oil and metallic-char in the presence of a microwave-heated bed of particulate-carbon through monitoring its temperature profile during the pyrolysis. These evaluations are important to examine if the metallic-char could act as a microwave-absorbent and heat up by microwave radiation, and if the metallic-char could be used as a catalyst in the pyrolysis of waste oil. Most existing waste oil pyrolysis studies focus on conventional electric-resistance-heated and electric-arc-heated pyrolysis ,  and , and there are very few studies about the pyrolysis products generated from microwave pyrolysis of waste oil, and in particular no similar studies have been reported on the application of metallic-char as a catalyst in microwave pyrolysis of waste oil; plasmodesmata study aims to rectify these deficiencies.