Oil helps cool an engine primarily by absorbing and transferring heat away from critical components.
Understanding Engine Oil as a Coolant
Engine oil serves multiple vital functions, one of which is cooling. As the provided reference states, oil cooling is the use of engine oil as a coolant, typically to remove surplus heat from an internal combustion engine. This is distinct from the primary liquid cooling system (using coolant like antifreeze), but oil plays a significant role, especially in areas not directly reached by the coolant jacket.
The Process: Heat Absorption and Dissipation
The process of how oil cools the engine involves a cycle of absorption and dissipation:
- Heat Absorption: The hot engine transfers heat to the oil. As oil circulates through the engine, it passes by and through extremely hot parts like pistons, cylinder walls, bearings, and turbocharger components. The oil picks up heat from these surfaces.
- Circulation: The heated oil then flows away from these hot areas.
- Heat Dissipation: According to the reference, the hot oil which then usually passes through a heat-exchanger, typically a type of radiator known as an oil cooler. This oil cooler works like a small radiator, allowing air or sometimes engine coolant to pass over tubes containing the hot oil. This transfers the heat from the oil to the surrounding air or coolant, cooling the oil down.
- Return: The cooled oil then returns to the engine to repeat the process, continuously absorbing more heat.
Here's a simplified look at the stages:
| Stage | Action | Role in Cooling |
|---|---|---|
| Absorption | Oil contacts hot engine parts. | Removes heat from components. |
| Circulation | Oil moves through passages. | Carries heat away from hot spots. |
| Dissipation | Oil passes through the oil cooler. | Releases absorbed heat to the air. |
| Return | Cooled oil returns to the engine. | Prepares for next heat absorption. |
Why Oil is Effective for Cooling
While not as efficient as dedicated liquid coolants, engine oil is effective at cooling specific parts because:
- It's Everywhere: Oil lubricates most moving parts within the engine, allowing it to reach areas that the primary coolant might not.
- Direct Contact: It's in direct contact with incredibly hot components like piston undersides (in some designs) and crankshaft bearings, where temperatures can be very high.
- Heat Transfer Properties: Oil has the capacity to absorb and carry heat.
In high-performance engines, turbocharged engines, or heavy-duty applications, dedicated oil coolers are essential to manage the higher heat loads generated. Without this cooling function, engine oil could overheat, degrade rapidly, and fail to lubricate properly, leading to severe engine damage.
