How can lubricants act as sealants in automobile engines?

In automobile engines, lubricants serve as a vital sealant by interposing a film between the piston rings and the cylinder walls. This fluid film helps maintain the necessary pressure and separation between these moving components, which is essential for efficient engine operation.12

Beyond their primary role of reducing friction and wear, lubricants in an engine also function as a coolant and a noise-reducing cushion. While grease is often used in other mechanical applications specifically to act as a seal against the loss of lubricant and the ingress of contaminants, the oil within the engine cylinder serves the critical purpose of sealing the combustion chamber to ensure optimal performance.13