Based on the physical arrangement of the carbon atoms, rubber process oils can be roughly divided into three fundamental groups: paraffinic, naphthenic, and aromatics. Every petroleum oil is a blend of different hydrocarbon groups, and it is categorized arbitrarily based on which hydrocarbon group predominates in the combination. The main component of ESPRO RPO 243 Oil is paraffinic rubber process oil that can be used as a plasticizer.