Oil Pan Drain Plug
The threaded bolt located at the bottom of the oil pan that is removed to drain old engine oil.
The oil pan drain plug is a threaded metal bolt located at the lowest point of the engine's oil pan. It is removed during an oil change to allow the old, contaminated engine oil to drain out of the crankcase. The plug is fitted with a crush washer or rubber seal to prevent leaks.
Because the drain plug is removed and reinstalled at every oil change, it is susceptible to wear. Over-tightening the plug is a common mistake that can strip the threads in the soft aluminum oil pan or on the plug itself. A stripped drain plug or a missing crush washer will cause oil to drip, risking low oil levels and engine damage.
During oil changes, the drain plug threads should be inspected, and the crush washer should always be replaced. If the oil pan threads are stripped, mechanics can install a thread repair insert (like a Helicoil) or a slightly oversized self-tapping plug as a repair solution.