I've a 2005 subaru forester with 107k miles. It has suddenly started burning oil. It needed a quart of oil after only 300 miles. Is it a head gasket problem? If yes, how much would it cost to fix it? At 102K miles I had timing belts replaced by the dealer. Is there any connection to that and oil leak? I've owned the car for 7 years and never had to add oil between oil changes before.