Subaru's are known for excessive oil consumption. Legacy with FB25 engine is no exception. Usually I change my oil every 8000km. I noticed a few times that the level was on the low side and had a slightly burnt smell. After about 5000km between changes, noticed the low oil light was on, and had to add almost a quart. Not sure at this time if it's an issue related to the oil leak from the cam carrier seal, or if it's from weak piston rings or something else. Not an immediate emergency, but will foul the spark plugs and cause carbon buildup in the engine over time. Recommend checking your sparks, removing carbon, and potentially installing a catch can. PCV valve also needs to be replaced frequently.