ICE-30 — Engine Lubrication

ASSUMPTION — This lesson covers the lubrication system conceptually; no specific oil viscosity grade is recommended.

In this lesson you will learn:

• The roles of lubrication
• The circuit components
• Viscosity and pressure importance

1. Why Lubrication?

The engine is full of moving, contacting metal surfaces (bearings, rings, cam-valve). Oil forms a thin film between them, reducing friction and wear.

FACT — Four roles: (1) reduce friction, (2) prevent wear, (3) carry heat (cooling), (4) carry contaminants to the filter.

2. Components

• Sump — the lower reservoir holding the oil.
• Oil pump — pressurizes oil into the circuit.
• Oil filter — traps particles.
• Oil passages — deliver oil to bearings and valvetrain.

FACT — In hydrodynamic bearings, an oil film forms between the rotating shaft and the bearing, preventing metal-to-metal contact — the basis of crank and cam bearings.

3. Viscosity and Pressure

FACT — Oil viscosity changes with temperature: too viscous when cold (hard to pump), too thin when hot (insufficient film). Multi-grade oils address this; oil pressure is also critical for bearing supply.

4. Summary

• Lubrication: friction, wear, cooling, cleaning.
• Components: sump, pump, filter, passages.
• Viscosity and pressure determine film formation.

5. Sources

• Bosch Automotive Handbook
• Heywood, Internal Combustion Engine Fundamentals

Next Lesson

• ICE-31 — Engine Sensors.