have you tried Vise- Grips??? If the bolt head is rounded off, these clamping pliers may work. If not, I would be afraid of welding on the oil pan due to possible fire, but glueing a good nut on top with JB Weld should work. IF the bolt is stripped inside of the pan and just turns, use a screwdriver for leverage while turning the Vise-grips or the bolt. Many oil change outlets will tighten hella out of the oil pan nut, and then they strip out. Once removed, you can use a larger-size bolt/plug. Think there's a previous post on that topic, too. JSM84