A process for producing a high viscosity functionalized metallocene polyalphaolefin (mPAO) fluid. The process includes providing a mPAO having a terminal double bond, said mPAO produced by the metallocene-catalyzed oligomerization or polymerization of an alpha-olefin feed; providing at least one of a substituted or unsubstituted alkyl thiol, aryl thiol, diphenylamine or naphthalene; and reacting, optionally in the presence of a catalyst or initiator, the mPAO having a terminal double bond with at least one of the substituted or unsubstituted alkyl thiol, aryl thiol, diphenylamine or naphthalene, under reaction conditions sufficient to produce the functionalized high viscosity mPAO fluid. The functionalized mPAO fluid has, as synthesized, a viscosity (Kv100) from 135 to 900 cSt at 100° C.; a viscosity index (VI) greater than 150; a pour point (PP) less than −25° C.; a molecular weight distribution (Mw/Mn) less than 2.0; a residual unsaturation (Bromine Number) less than 2.0; and a glass transition temperature Tg less than −30° C.