low oil and driving hard, sounds very much like a spun bearing situation, as stated before it's a minimum if checking the crank bearing to see if it's ben scored (probably will have been which means regrind/swapped crank and the offending con rod too). no amount of service will make that go away unfortunately, do not drive it anywhere or run the engine. it will only make it worse. the earlier you strip it down and check the more of the engine can be saved.