there's a subtle tick i can hear while my cars running. Sounds to me like a bad lifter, or maybe there's some sludge buildup around a valve. But someone told me that they had the same problem, but in a Cadillac motor. He changed the oil, added some transmission fluid to the oil; ran it at idle for a bit, and drained the oil mix out then added fresh. Has anyone tried this, or heard of this method to clean out gunk in their motors?