I sometimes get asked how seal swell agents work and while doing some research on the topic, I came across this video from Lubrizol which shows how an oil's impact on seals is evaluated. The test shown here isn't the only one used, but it is one of the main ones.
Basically after being exposed to oil after a long period of time (a week at elevated temperature), the seal coupon is stretched to see if it has changed since new. High Mileage engine oils contain ingredients designed to soften older and harder elastomers and bring them back to similar levels of performance to new material using what is shown in these tests to evaluate the performance.
Hope you like the video as much as I did!
Basically after being exposed to oil after a long period of time (a week at elevated temperature), the seal coupon is stretched to see if it has changed since new. High Mileage engine oils contain ingredients designed to soften older and harder elastomers and bring them back to similar levels of performance to new material using what is shown in these tests to evaluate the performance.
Hope you like the video as much as I did!