Biofilms are said to feed on oil contents found in synthetic rubber compounds used in sealing, pipeline and water separation valve applications but the extent of the degradation is not known. This work provides a way of characterizing the microscopic degradation as a result of the microbial adsorption on the rubber compound surfaces. Pseudomonas aeruginosa bacteria were grown on ethylene propylene diene monomer (EPDM) rubber compounds having increasing oil amounts. Results revealed that the microorganisms adhered and fed more on the oil-rich surfaces than those with less oil or oil-less surfaces and promoted smooth morphologies with reduced surface roughness values. Furthermore, elongation at break results from tensile test measurement showed an increase in stiffness with increasing oil amount after the bacteria degradation. This work supports rubber engineers when selecting rubber compounds for water contact applications.