An additive system for a polyvinyl chloride formulation for improved processability while maintaining thermal stability of the formulation, and having a low-water-blush haze and low extractability in an aqueous media, the additive system including a primary stabilizer which is a Lewis acid metal compound selected from the group consisting of organo-tin compounds and organo-zinc compounds, a secondary stabilizer selected from the group consisting of epoxide compounds having less than approximately 5.2 oxirane groups per molecule; and, an external lubricant for lubrication of the PVC formulation, wherein a critical ratio of the primary stabilizer to the secondary stabilizer maximizes thermolytic color stability while limiting generation of excessive build-up, plate-out, dark particles during the processing of the polyvinyl chloride formulation. And wherein the invention provides concentration levels of the stabilizers and an oxirane per molecule content of the secondary stabilizer which minimizes the extractbiles in aqueous media.