A process for the preparation of dynamically vulcanized thermoplastic elastomers comprising melt processing under shearing conditions in melt reaction extruder, A) at least one thermoplastic resin, B) at least one vulcanizable gas-phase elastomer having a Mooney viscosity (ML.sub.1+4(125° C.)) of from about 65 to about 450, C) a curing agent or agents, and D) process oil, wherein said process oil D) is added to the extruder in at least three oil injection positions located a) at least one location before or within the first 15% of the total length of the extruder; b) at least one other location prior to, at or within 10% total extruder length after the onset of the vulcanization of said gas-phase elastomer; and c) at least one location subsequent to the location of the point at which the vulcanization of said gas-phase elastomer is substantially completed.