Oil spray tubes in the engine block are designed to cool which area?

• A. Piston crown
• B. Underside of the piston
• C. Cylinder walls
• D. Valve train

Answer: (B)

Oil spray tubes are designed to remove heat from the piston where it experiences the most thermal stress—the underside of the piston. The heat from combustion is transferred through the piston, and spraying oil onto the lower surface absorbs that heat. The oil then carries the heat away to the sump, helping keep the piston cooler, reducing thermal expansion and wear on the piston and rings. Cylinder walls and the valve train have their own cooling and lubrication paths, so direct spray to the underside of the piston is the targeted cooling method.