I don't quite understand the question. Do you mean your oil is always clean, or do you mean that the level is always the same?
If it is the latter, it should stay the same. Unless I am wrong on this, but the level should stay the same unless you are buring oil or you have a leak.
If it is the latter, it should stay the same. Unless I am wrong on this, but the level should stay the same unless you are buring oil or you have a leak.