I bought a new oil pan bolt from NAPA and it was undersized just enough that it would not seal. I ended up putting a small wrap of plumbers tape right under the head of bolt to seal the last few threads along with a rubber gasket from the hardware store that I replace every time I change the oil. The tape works in a pinch, but you don't want it getting inside the oil pan so make sure it all comes out with the bolt. I should have probably went to the wrecking yard and grabbed an oem bolt off something else and it would have fixed it.