This past weekend I had by '10 OB, 66,xxx miles, up in the NC mountains for some skiing. I noticed the sweet smell of antifreeze burning when I got out from driving a time or two. I had a shop take a look Tuesday and they said they didn't see obvious leaks but the radiator was low and they saw "staining" around the left front cylinder. I have an extended warranty through Subaru and so I took it to the dealer to have it gone over. Said they filled it full of antifreeze and let it run for 30 minutes at idle and also revving it, and the levels did not change. They also said they didn't see any obvious leaks. I had them do a pressure and leak down test and they said this showed nothing as well and everything was performing normal. Anybody had a similar experience or have any ideas? Could harder driving in the mountains have caused it to just burn up antifreeze? It has shown no performance issues and has not had the burning smell since. Never seen a drop on the pavement either.