Thermoplastic compositions are provided containing a saturated hydrocarbon amine oxide and stabilizer compositions are provided containing a saturated hydrocarbon amine oxide and a second stabilizer. The thermoplastic compositions exhibit good melt flow rate stability during processing and are useful for making molded and extruded articles. The stabilizer compositions are useful for addition to thermoplastics for the stabilization thereof. A method is also provided for stabilizing thermoplastic compositions and involves admixing a hydrocarbon amine oxide with a thermoplastic resin. The saturated hydrocarbon amine oxides are preferably trialkyl amine oxides. The thermoplastic resin is preferably a polyolefin resin.