What is the primary function of engine oil?

What is the primary function of engine oil?

• A. Cooling of combustion chamber.
• B. Lubrication of moving parts, cooling, sealing, and cleanliness to reduce wear.
• C. Generating thrust.
• D. Fuel delivery to cylinders.

Answer: (B)

Engine oil's primary function is to lubricate moving parts, creating a protective film that reduces friction and wear between components such as bearings, gears, and piston rings. This lubrication is essential because metal-to-metal contact at operating temperatures would quickly wear parts and reduce efficiency. Oil also helps carry heat away from hot bearing surfaces to the oil cooler, contributing to cooling; it seals small gaps around piston rings and bearing surfaces to limit gas blow-by and maintain compression; and it keeps the engine clean by suspending dirt and particulates and carrying them to the oil filter. The other choices describe functions that belong to other systems: cooling the combustion chamber is handled by the cooling system, generating thrust is the job of the propulsion system, and delivering fuel to cylinders is the function of the fuel system.

Engine oil's primary function is to lubricate moving parts, creating a protective film that reduces friction and wear between components such as bearings, gears, and piston rings. This lubrication is essential because metal-to-metal contact at operating temperatures would quickly wear parts and reduce efficiency. Oil also helps carry heat away from hot bearing surfaces to the oil cooler, contributing to cooling; it seals small gaps around piston rings and bearing surfaces to limit gas blow-by and maintain compression; and it keeps the engine clean by suspending dirt and particulates and carrying them to the oil filter. The other choices describe functions that belong to other systems: cooling the combustion chamber is handled by the cooling system, generating thrust is the job of the propulsion system, and delivering fuel to cylinders is the function of the fuel system.