An activated carbon, disclosed as useful in purification and decolorization of hydrocarbon fuel, particularly gasoline, is characterized by inclusion therein of polymerized phosphoric acid or reduced transition metals. Phosphoric acid may be added to a non-phosphoric acid-activated carbon (such as steam activated coal-based) prior to the subsequent heat treatment or one can take advantage of residual phosphoric acid present in, for example, a phosphoric acid-activated wood-based carbon. Similarly, transition metals such as copper may be added to an activated carbon in a salt form in addition to whatever is already present therein as impurities. The conversion of phosphoric acid to a polymerized phosphate content or reduction of transition metals to a reduced form results from the activated carbon having been treated with inert gas or carbon dioxide at from about 1200° F. to about 1800° F. for at least 5 minutes. Alternatively, the conversion of phosphoric acid to a polymerized phosphate content can occur during phosphoric acid activation of carbon at activation temperatures in the range of 1150°-1600° F.