🔍 Key Concepts

• lubricating oil passages in crankshafts and where they lead • relationship between main bearings, connecting rod bearings, and piston pin bushings • how oil flows from the engine block through the crankshaft to moving parts

💭 Think About

• Think about which parts actually receive oil that has traveled through drilled passages in the crankshaft itself, not just through the engine block or other galleries. • Ask yourself: once oil enters the crankshaft from the main bearing area, which components must it reach next to prevent metal-to-metal contact during rotation? • Consider whether each listed bearing/bushing relies on crankshaft rotation to distribute oil, or if some can be fed directly without going through the crankshaft.

✅ Before You Answer

• Verify which components are directly served by internal oil passages bored inside the crankshaft. • Check how oil reaches the connecting rod big-end bearing and then, if applicable, the piston pin bushing on typical trunk piston diesel engines. • Confirm whether each item listed can be (and commonly is) pressure-fed via crankshaft drillings, not just splash or spray lubrication.