A method of producing submicron carbon particles from oil ash. The method comprises pyrolyzing the oil ash to produce a pyrolyzed oil ash and milling the pyrolyzed oil ash to produce carbon particles having a mean particle size in the submicron regime. The method produces submicron carbon particles which have a very high carbon content (90 to 99 atom %) and a very low content of oxygen, the particles having a ratio of carbon to oxygen ratio of 10:1 to 99:1. The size of the particles may be controlled by the duration of the milling. The submicron carbon particles are devoid of functionalities containing carbon-oxygen double bonds as measured by Raman spectroscopy and X-ray photoelectron spectroscopy (XPS).