Will it leak oil if the drain plug washer is forgotten?

[LucyRose]

Oil may seep out when the seal is not tight, but it won't leak if the seal is tight. Here are the relevant details: 1. The washer added before tightening the drain plug serves as a seal. Forgetting to add the washer can easily lead to oil leakage, which may affect the engine's operation. The contact surfaces between the drain plug and the oil pan are mechanical and cannot be perfectly flat. Without a washer, they cannot achieve a complete seal. The washer fills the gaps between them, ensuring a sealed state. 2. The washers commonly used are made of aluminum. When tightening the screw, the soft aluminum material easily deforms to fill the gaps. However, the tightening force must be properly controlled. Too little force may result in insufficient deformation of the washer, failing to fill the gaps and causing leakage.