My wife has a 2008 Impreza with the 2.5 engine. We bought it new and it currently has around 50k on it. After reading all these oil threads I see many people have to replace the head gaskets around 100k. I was curious to get some background on this and other things I can expect. Typically what is the cost for head gasket service? So far the car has been great. I do most all the maint myself including the 30k spark plugs. I started the car on m1 for the first couple years and since has been pp. I am about to drop in some castrol edge gold that I got on sale soon though.