Dynamic vulcanizates of an engineering thermoplastic ("plastic"), e.g. a polyamide or polyester, with acrylate rubbers having dissimilar functional groups are prepared with a metal fatty acid salt in the absence of a conventional curative, provided the rubbers are molecularly intermixed. An acrylate rubber with halogen functionality ("AcrRubHal") is thus crosslinked in a single mixing stage with an acrylate rubber having carboxyl, hydroxyl or epoxy functionality ("AcrRubX") in a "plastic". Quaternary ammonium salts and tertiary amines do not function as curatives, as one might expect. But a metal fatty acid salt, preferably a metal stearate or oleate and concentrates thereof effectively crosslink the rubbers. TPVs produced without conventional curing agents are relatively "soft", but have highly desirable low temperature physical properties and oil resistance.