Kevin,
Since it sounds like you might not have access to an original tensioner and there's been nothing conclusive posted on the thread, I propose you do the following test. Put the new tensioner in a glass jar with 50/50 mix of old and new oil. Since you live in sunny San Diego, let it sit in the sun for a week. It's not going to get to operating temperature, but it will probably hit 100 with direct sun. That plus the longer term exposure and cooling down at night should give you some indication. Just take some measurements ahead of time so you can detect even smaller changes in dimensions. HTH
Since it sounds like you might not have access to an original tensioner and there's been nothing conclusive posted on the thread, I propose you do the following test. Put the new tensioner in a glass jar with 50/50 mix of old and new oil. Since you live in sunny San Diego, let it sit in the sun for a week. It's not going to get to operating temperature, but it will probably hit 100 with direct sun. That plus the longer term exposure and cooling down at night should give you some indication. Just take some measurements ahead of time so you can detect even smaller changes in dimensions. HTH