Which lubrication method is normally used for lubricating connecting rod pins?

Which lubrication method is normally used for lubricating connecting rod pins?

• A. Grease
• B. Oil pressure feed to the pin
• C. Dry lubrication
• D. Splash oil

Answer: (D)

Connecting rod pins are lubricated by splash oil because the pin undergoes rapid, combined sliding and rotating motion within the crankcase. When the crankshaft spins, oil is thrown up and splashed around the underside of the piston and into the area of the pin, forming a lubricating film on the bearing surfaces without needing separate oil lines. This approach is simple, reliable, and well-suited to the engine’s normal lubrication system, where the crankcase oil serves as the source of lubrication. Grease wouldn’t flow quickly enough at operating temperatures and speeds, and it can smear or squeeze out of the bearing surfaces. Oil pressure feed to the pin adds complexity with extra passages and seals near a highly vibrating area, which isn’t necessary in most engines. Dry lubrication would wear quickly under the high-frequency motion of the pin.

Connecting rod pins are lubricated by splash oil because the pin undergoes rapid, combined sliding and rotating motion within the crankcase. When the crankshaft spins, oil is thrown up and splashed around the underside of the piston and into the area of the pin, forming a lubricating film on the bearing surfaces without needing separate oil lines. This approach is simple, reliable, and well-suited to the engine’s normal lubrication system, where the crankcase oil serves as the source of lubrication.

Grease wouldn’t flow quickly enough at operating temperatures and speeds, and it can smear or squeeze out of the bearing surfaces. Oil pressure feed to the pin adds complexity with extra passages and seals near a highly vibrating area, which isn’t necessary in most engines. Dry lubrication would wear quickly under the high-frequency motion of the pin.