I suspect my monster-in-law's Subaru has a head gasket leak (big problem with certain Subies as I found out) as I'm adding approx. 10-12 ounces of coolant between 3,000 mile oil changes. I've ordered the test kit from Blackstone and I'm wondering if I need to wait longer than 3,000 miles for this size coolant leak to show up good on a UOA. I'm Doing this so it can be taken care of under the powertrain warranty which will expire soon as the car has 58,000 miles and the warranty expires at 60,000. Thoughts and comments welcome!