My daughter has this 6 cylinder engine in her 2008 Legacy. My 4 cylinder 2007 Legacy needed head gaskets replaced after I detected small oil leak (but no other issues) at 90k miles. I was told this is quite normal for this engine. My question is whether it is also normal and at what miles for the 3 liter engine. I have heard a range of 120-180k for the 3 liter.