Subaru has an additive to temporarily solve problem. Is 100 thousand miles to early to leak?
We’ve had many posts on this problem Subarus, and many were at less than 100,000 miles. As to the additve, I would be sceptical as to that being a permanent solution.
Subaru has an 8 year/100,000 warranty for the issue.
There is a known issue with the 2.5L non-turbo engine up to early 2004 with this issue.
The additive is basically Subaru branded stop leak. I think they are nervous now and basically have it added at all coolant changes which are IMHO too often for pocket (every 30k) on Subaru’s.