Diesel Engine Lubricating Oil Functions and Properties

When moving components of a diesel engine, such as shafts and pistons, rotate or slide against bearings and cylinder walls, friction occurs between their contact surfaces. Direct metal-to-metal dry friction not only consumes substantial power—greatly reducing the engine’s effective output—but also causes rapid wear of moving parts. This friction generates intense heat, leading to surface scorching, seizure, or even severe engine damage. To mitigate this, lubrication is critical: a film of lubricating oil is introduced between the friction surfaces, transforming dry friction into liquid friction between oil molecules. This significantly minimizes power loss and alleviates component wear.

Core Functions of Diesel Engine Lubricating Oil

1.Lubrication: As the primary function, it maintains a stable oil film between moving surfaces to reduce friction losses and prevent mechanical wear.

2.Cooling: Absorbs and carries away heat generated by friction, ensuring operating surfaces do not overheat.

3.Cleaning: Flushes away contaminants like dust and metal particles from friction surfaces, keeping them clean.

4.Sealing: The oil film between the piston and cylinder liner enhances combustion chamber sealing.

5.Corrosion Protection: Coats metal surfaces to isolate them from air, preventing oxidation and rust.

6.Neutralization: Counteracts acidic effects from sulfur compounds in fuel, protecting cylinder liners, pistons, and crankshafts from corrosion.

Key Performance Characteristics of Lubricating Oil

1.Viscosity: The foundation of oil film lubrication. Proper viscosity is crucial: low viscosity thins the oil film, increasing leakage, reducing load-bearing capacity, and accelerating wear; high viscosity hinders rapid spreading across friction surfaces, making it difficult to form a continuous, uniform film and increasing engine friction losses. Thus, selecting the correct viscosity grade is essential.

2.Acid Value: Measures the acidity of the oil, defined as the milligrams of potassium hydroxide (KOH) required to neutralize one gram of oil. Lubricating oil naturally contains organic acids, and residual inorganic acids may remain from the refining process.

3.Oxidation Stability: Refers to the oil’s resistance to oxidation by air, determined via specialized testing. During circulation, oil continuously contacts air, gradually oxidizing and deteriorating. Temperature significantly impacts oxidation rate: for every 10°C increase in oil temperature, the oxidation rate doubles.

4.Demulsibility: When seawater or freshwater contaminates the oil, emulsification occurs. Emulsified oil traps water, forms foam, disrupts oil pressure, and causes engine damage. Additionally, undissolved impurities remain suspended, contaminating friction surfaces and exacerbating wear.

5.Total Base Number (TBN): Indicates the alkalinity of additive-containing lubricants, expressed as milligrams of KOH equivalent to the alkaline substances in one gram of oil. Sulfur in low-quality fuel (e.g., Heavy Fuel Oil, HFO) converts to sulfur dioxide (SO₂) during combustion. To control and prevent corrosive wear, diesel engine lubricants must retain sufficient alkalinity to neutralize acidic by-products from sulfur combustion.

6.Dispersancy: An indicator of the oil’s ability (via additives) to clean gum and carbon deposits from component surfaces, dispersing them into small particles for suspension. This prevents insoluble impurities from depositing on moving parts, ensuring they do not interfere with normal engine operation.

Dingbo Power was founded in 1974 and is one of the earliest manufacturers of generators and diesel generator sets in China. If you want get more information, please feel free to send email to [email protected] we will pay highly attention on your question.