What device forces oil under pressure against the rotating connecting rod?

The device that forces oil under pressure against the rotating connecting rod is typically an oil pump, and in this context, an ejection pump is often used to describe such a device. The primary function of this pump is to circulate oil throughout the engine to ensure proper lubrication of moving parts. By forcing oil under pressure, it helps to minimize friction and wear on components like the connecting rod, which can be subject to significant stress during engine operation.

Other components mentioned, such as the oil filter, play a crucial role in removing contaminants from the oil to ensure that the lubricating system functions efficiently, but they do not actively pump the oil. The oil cooler is designed to regulate the temperature of the oil but, again, does not have a role in pressurizing it. A pressure gauge simply measures the oil pressure within the system but does not influence the movement of oil itself. Therefore, the ejection pump is the correct device responsible for pressurizing and delivering oil to critical engine components like the connecting rod.