It is often assumed that green petroleum coke behaves as an inert material in cocarbonization with coking coal blends and has no active behavior on the important thermoplastic properties of the coal blend. This paper investigates that assumption. The objective of this study is to clarify effects arising when different petroleum cokes are added to a single coal or an industrial blend. The effects studied include changes during the pyrolysis stages of the cocarbonization, using a bituminous coal. This was done to study if petroleum coke is totally inert at the plastic stage of a given coal or there is an influence at the plastic stage. A further aim is to show how conventional and nonconventional techniques for petroleum coke characterization relate to its activity with the plastic stage of coal. A range of six petroleum cokes was used. The petroleum cokes were studied in terms of (a) optical texture, (b) FTIR spectroscopy, (c) hydrogen donor ability, (d) thermogravimetric analysis of the pyrolysis stage, (e) free-swelling index, and (f) thermoplastic properties of blends made up of a bituminous coal and petroleum coke. Evidence for a significant activity of some petroleum cokes was assessed using the above techniques, which can be considered as nonconventional in petroleum coke characterization. A good correlation among the parameters obtained from the above techniques/methods was found, indicating that the presence of unreacted and partially carbonized material, the hydrogen donor ability, the relative proportion of methyl and methylene groups, the amount of volatile matter released at a temperature range between 400 and 500 degrees C, the temperature of maximum volatile matter evolution and, finally, the agglomeration degree of petroleum cokes can be considered as important factors in the plastic properties of cocarbonization systems with coking coals.