is any petroleum process oil used in the manufacture of rubber and rubber products. Rubber oils may be used either as rubber extender oils or as rubber process oils. Rubber extender oils are used by the synthetic rubber manufacturer to soften stiff elastomers and reduce their unit volume cost while improving performance characteristics of the rubber. Rubber process oils are used by the manufacturer of finished rubber products (tires, footwear, tubing, etc.) to speed mixing and compounding, modify the physical properties of the elastomer, and facilitate processing of the final product.

Also see rubber oil classification.