Synthetic oils

Care is very crucial to what happens to the oil. But there is no way after 160K you would have no sludge. Even with synthetic, at that point, you'd be bound to develop some sludge. Unless maybe you idle your car 160K, you'll get sludge. If you've found a way to get an engine 160K with NO sludge, you have a magical power and should be rich by now.