FAA Powerplant Written Practice Test

How is oil collected by the piston oil ring returned to the crankcase?

1. Through the valve cover

2. Through holes drilled in the piston oil ring grooves

3. Through a pump mechanism

4. Through the oil filter

The correct answer is: Through holes drilled in the piston oil ring grooves

The piston oil ring is designed specifically to manage the amount of oil that comes into contact with the cylinder wall. As the pistons operate, the oil ring collects excess oil from the cylinder wall and prevents too much oil from entering the combustion chamber, which helps reduce oil consumption and prevent fouling of the spark plugs. The correct process for returning the oil collected by the piston oil ring to the crankcase involves specific holes drilled in the piston oil ring grooves. These holes allow the excess oil to flow back down the piston and into the crankcase as the piston moves down during its stroke. This mechanism is crucial for maintaining the proper lubrication of engine components and ensuring that oil levels remain sufficient for optimal engine operation. In contrast, options like returning oil through the valve cover, a pump mechanism, or the oil filter do not pertain to the role of the piston oil ring in managing and returning oil. While oil does circulate throughout the engine via these other pathways, the direct pathway for oil collected by the piston oil ring is through the grooves specifically designed for that purpose, making the holes in the piston oil ring grooves the correct answer.