88
Differences In Commercial Motor Oils and The Effects On Sealing Materials
David Clark, P.E.
Freudenberg-NOK Sealing Technologies
Sealing materials are tested and validated in Original Equipment Manufacturer (OEM) factory fill motor oils. However, the consumer may not continue to use the recommended motor oil in favor of convenience or lower cost oils. The consumer also may not change the motor oil as frequently as the OEM recommends. This study evaluated the changes in physical properties of common sealing polymers – FKM, HNBR, ACM, AEM – when exposed to factory fill 5W-30 oil or ten commercially available “equivalent” grades.
Fluid exposure procedures were developed to simulate a new car purchase followed by a change in oil brand and/or a long wait between oil changes. The volume swell of all polymer types approached steady state after one week of fluid exposure and did not vary significantly between oil brands. However, mechanical properties continued to degrade over time and showed a wide range of results depending upon oil brand and polymer type. Given so many uncontrollable consumer actions (oil type and change frequency), there is a risk for sealing manufacturers to make warranty and lifetime predictions based only on OEM factory fill motor oil testing.