I had the same problem on a new Subie. Go to a local hardware store and go over to the nuts / bolts section. Look in the clip boxes (there may be several). I used one that worked perfectly.
I have a 2005 Outback 2.5 limited and have been using synthetic oil since the first oil change. However, I noticed the car using about 1 1/2 qts every 4000 miles. I drive about 4000 miles per month, mostly interstate.
Is this normal with synthetic?