A thermostabilized thermoplastic molding composition includes a) a thermoplastic polyamide composition which consists of a blend of at least two polyamides. The at least two polyamides include a1) at least 50 mass %, relative to the total mass of the thermoplastic polyamide composition, of a first polyamide (PA-1) selected from the group consisting of polyamide-4,6, polyamide-6,6 and semi-aromatic polyamides and mixtures thereof; and a2) an amount of 1-50 mass %, relative to the total mass of the thermoplastic polyamide composition, of a second polyamide (PA-2) selected from the group consisting of polyamide-6 and copolymers thereof. The composition also contains b) 0.001-3 mass %, relative to the total mass of the thermoplastic polyamide composition, of a copper salt; and c) 0.01-10 mass %, relative to the total mass of the thermoplastic polyamide composition, of iron oxide. The molding composition exhibits reduced deterioration when exposed to an elevated temperature of 230° C. for a prolonged time period of 1000 hours as compared to an identical molding composition including a Cul/KI stabilization system but not including the iron oxide.