🔍 Key Concepts

• Viscosity vs. temperature relationship for lubricating oil • How pressure and shear in bearings affect oil temperature in the system • Location and function of the lube oil cooler and main lube oil pump in a typical circulation diagram

💭 Think About

• In an operating system under normal load, where will the lube oil be coolest, and where will it be hottest? • How does a change in temperature affect viscosity: does hotter oil become thicker or thinner? • Trace the oil flow path through the system and think about where the oil has just been cooled and where it has just absorbed heat from bearings and machinery.

✅ Before You Answer

• Verify which component (cooler, pump discharge, bearing wedge) will have highest oil temperature during normal operation. • Confirm that higher temperature = lower viscosity and lower temperature = higher viscosity for lube oil. • Check the usual sequence of flow: sump → pump → cooler (or cooler → pump, depending on design) → engine bearings → return, and decide at which listed point the oil would be coldest.