Which type of engine lubrication involves the use of an oil reservoir below the engine?

Wet sump lubrication is characterized by having an oil reservoir that is situated below the engine. In this system, oil is stored in a sump at the bottom of the engine block, from where it is pumped to the various moving parts of the engine as needed. This method is commonly used in many automotive applications due to its simplicity and effectiveness, as it allows for easy oil circulation and maintenance.

In contrast, dry sump lubrication features an external oil reservoir located away from the engine itself, which can help maintain a consistent oil supply under high-performance or high-speed conditions by preventing oil starvation. Splash lubrication relies on the engine components themselves to distribute oil through splashing, and it often does not use a dedicated oil pump. Forced lubrication, while it does involve pumping oil, does not necessarily indicate the position of the reservoir relative to the engine. Each of these systems serves different applications and has its specific advantages, but the defining characteristic of wet sump lubrication is the location of the oil reservoir below the engine.