Get a good flashlight and start checking things, sure its not a rod knock? Thats a serious oil loss, check all lines, cooler, with a loss that severe you ought to be able to easily see a very wet fresh trail of oil drooling out somewhere off the engine. Also check filter housing, misplaced o-ring on lid or loose stud can cause leaks. IP on some versions has some plastic oil lube lines to it, check them too.