🔍 Key Concepts

• hydrodynamic vs boundary lubrication in bearings • effect of oil temperature and viscosity during different operating phases • how oil film formation changes between starting, warm-up, and load changes

💭 Think About

• At what point in operation is the oil film LEAST fully developed on the bearing surfaces? • When is the oil at its least ideal viscosity for proper lubrication in a cold engine? • Which condition makes metal-to-metal contact most likely before full oil pressure and flow are established?

✅ Before You Answer

• Identify when full oil pressure and flow are first reliably established in the system • Compare oil temperature and viscosity at each option (cold vs warmed vs under load changes) • Decide at which phase the risk of metal-to-metal contact on bearings is greatest