🔍 Key Concepts

• Hydrodynamic lubrication and how an oil film is formed between bearing and journal • What conditions cause metal-to-metal contact in bearings • How oil pressure and oil flow behave at different stages of engine operation (start, warm-up, running, shut-down)

💭 Think About

• At which point in operation is the bearing rotating but the full oil film has NOT yet been fully established? • When is oil temperature, viscosity, and oil pressure least stable or least favorable for forming a protective film? • Which stage presents the greatest risk of momentary loss of oil supply or delayed oil delivery to the bearings?

✅ Before You Answer

• Identify when oil pressure first comes up and when it is most likely to be insufficient for full-film lubrication • Consider when bearing surfaces are most likely to touch directly before the oil wedge is built up • Think about which phase is emphasized in engine manufacturer procedures as needing special care for lubrication protection