Definition
The part of an engine's lubrication system that collects oil after it has lubricated and cooled the engine's internal components and returns it to the oil tank or reservoir. In a dry-sump engine, scavenge pumps pull the used oil from the bottom of the engine and from bearing cavities, then push it back through the oil cooler and into the tank, where it can be circulated again by the pressure subsystem.
Plain English
The 'return side' of the oil system. After oil has done its job inside the engine, the scavenge subsystem pumps it out of the engine and sends it back to the tank to be reused.
Context Anchor
Seen in aircraft engine oil system descriptions, especially in maintenance training for turbine engines and dry-sump oil systems.
Derivation
Scavenge comes from an old word meaning 'to collect or gather what is left behind.' In engines it captures the idea of sweeping up the used oil from places it has pooled and bringing it back to be used again.
Why Pilots Care
If the scavenge subsystem fails or underperforms, oil pools inside the engine instead of returning to the tank. This can starve the pressure side of oil, cause overheating, and lead to engine damage even though the tank may still appear to hold oil.
Analogy
It is like a drain pump in a basement. The pressure side sends the fluid where it is needed; the scavenge side collects it afterward and pumps it back out.
Grounding Statement
Picture oil being sprayed onto hot moving engine parts, then quickly collected and pumped back out before it can sit there and overheat.
Intuition Check
Scavenge does not mean the system is searching randomly for oil. Here it means collecting used oil from specific engine areas and returning it to the oil system.
Example Sentence 1
The scavenge subsystem uses multiple pumps to draw oil from the engine sumps and return it to the oil tank.
Example Sentence 2
A clogged scavenge line caused oil to pool in the bearing compartment until the pump was replaced.