That time and temp has not been determined yet but. We have seen severl engines apart with burned edges of pistons and heavily damaged cylinders and rings. The problem is damaging and then opening up the engine to actually see what happened at that time. Most continue to run till other issues come up like knocks or loss of compression or a piston cracks and drops thru the pan or the block. then determining what and when it happened is lost. Its almost like driving till you run out of fuel. Just how far are you going to push it till you switch to a full tank.