So far since my last oil change I haven't had to add,always on the same mark. But I have found the level lower in the past like one time last year I had to add maybe 1/4 of a quart at one point. A week ago i got home from work and found a bunch of oil leaking out of the air filter . I had been driving it hard for a couple days though so that could be normal. Don't worry man , as mentioned keep the level between the lines and your golden,there is no mystery involved.