Abstract: The disclosure is generally directed to the field of optimizing feedstock in pyrolysis systems. A method of obtaining pyrolysis oil from a feedstock comprising rubber comprises the steps of: providing a feedstock comprising rubber; milling the feedstock, thereby providing particles; and pyrolyzing the particles in a vessel; wherein the median size of the particles is from about 0.5 mm to about 15 mm, optionally from about 0.5 mm to about 12 mm, optionally from about 0.5 mm to about 9 mm, optionally from about 0.5 mm to about 6 mm, optionally 15 mm or smaller, optionally 12 mm or smaller, optionally 9 mm or smaller, optionally 6 mm or smaller. The feedstock optionally comprises a plurality of tires.