How to Prevent Diesel Generator Engine Oil Deterioration?

As an important power equipment in industrial production, construction, emergency power generation, and other scenarios, the stable operation of diesel generators is crucial to ensuring the smooth progress of various activities. However, as the key lubricant of diesel generators, the quality and performance of engine oil are directly related to the lifespan and operating efficiency of the engine. If the engine oil deteriorates, it will not only reduce engine performance but may also cause serious mechanical failures. This article will deeply explore the causes of diesel generator engine oil deterioration and provide corresponding preventive and coping strategies.

During the operation of a diesel generator, engine oil deterioration is a common and important problem. Engine oil deterioration not only reduces the performance of the engine but may also lead to serious mechanical failures. The following are the main causes of engine oil deterioration.

During the operation of the diesel generator, if problems such as a perforated wet cylinder liner, damaged cylinder liner water ring, damaged oil cooler, damaged cylinder gasket, or damaged cylinder head occur, coolant may seep into the engine oil. This will lead to emulsification and deterioration of the oil. The method of judging this problem is to observe whether the coolant is abnormally consumed and whether the engine oil shows abnormality due to water emulsion.

Overheating of the diesel engine is another major cause of engine oil deterioration. The main causes include insufficient coolant, excessive scaling in the cooling system, pump failure leading to interruption of coolant circulation, debris blocking the radiator, radiator cap and thermostat issues, loose or broken fan belts, long-term heavy load operation in high-temperature seasons, carbon deposits in the combustion chamber, and insufficient oil in the lubrication system. When the oil temperature rises, its antioxidant stability deteriorates, accelerating thermal decomposition, oxidation, and polymerization, leading to rapid oil deterioration.

When the diesel engine is working, combustible gas and exhaust gas will pass through the gap between the piston rings and the cylinder wall into the crankcase. If the piston rings are severely damaged, this phenomenon will be more serious. Condensed fuel vapor entering the crankcase will dilute the engine oil; acidic substances and water vapor in the exhaust gas will corrode parts; meanwhile, the oil will gradually dilute, age, and carbonize, reducing its performance. In addition, the gases entering the crankcase will increase its temperature and pressure, causing oil leakage from oil seals and gaskets. Therefore, diesel engines are equipped with a vent pipe to keep the pressure inside and outside the crankcase balanced, thereby extending the oil life. However, when crankcase ventilation is poor or there is air resistance, it will accelerate oil oxidation and deterioration.

When changing oil, if the lubrication system is not cleaned, the crankcase is not carefully washed, the oil filter or oil cooler is not thoroughly cleaned, or the oil filter sealing gasket is missing, then even after adding new oil, the oil will soon be seriously contaminated by residual pollutants, thereby accelerating its deterioration.

After understanding the main causes of engine oil deterioration, let us now look at how to prevent and cope with oil deterioration to ensure stable operation of diesel generators and extend their service life.

Check Oil Contamination Level: When checking the oil level, pay attention to the contamination level of the oil. The oil on the dipstick should not show discoloration (except for normal blackening). When the oil reaches its mileage interval or oil change index, it should be replaced in time.

Use Suitable Engine Oil: The compression ratio of diesel engines is more than twice that of gasoline engines, and the effects of high temperature and high pressure on its main components are much greater than gasoline engines. Therefore, more anti-corrosion agents should be added in the refining process of diesel engine oil to form a protective film on the surface of bearings, reduce corrosion, and improve wear resistance. Different brands of engine oil not only differ in viscosity grade but also in chemical composition, mainly due to different types and amounts of additives. Normally, engine oil types and quality grades are classified by the type and amount of additives. Since different types of additives have different chemical properties, oils with different additives should not be mixed; otherwise, chemical reactions may occur between additives, causing a sharp decline and rapid deterioration in oil performance.

Check Oil Quality: Common methods for checking oil quality include oil spot comparison, viscosity comparison tests, and laboratory analysis. Using the oil spot method, drop a drop of new oil and a drop of used oil of the same type on clean white paper, and compare changes. If the used oil shows many hard asphalt and carbon particles in the black spot, it means the oil filter is not effective, but not necessarily that the oil has deteriorated. If the black spot is small and lighter in color, with a large surrounding yellow halo and indistinct boundaries gradually diffusing, it means detergents in the oil are not yet exhausted, and the oil can continue to be used. If the black spot is large, the oil is dark brown and uniform without particles, with a clear boundary between the black spot and the yellow halo, it means the detergents have failed, the oil has deteriorated, and it should be replaced promptly.

Start the Diesel Engine: When changing oil, start the engine and let it run until it reaches normal operating temperature (above 80℃), then shut it off, and drain the old oil from the oil pan and filter while hot. Some diesel engines have magnetic drain plugs, which should be cleaned of iron filings after draining before reinstalling.

Use Vacuum Oil Change Equipment: If possible, use vacuum oil change equipment, which can suck out the old oil more thoroughly.

Flush the Lubrication System: If the drained oil is dirty, flush the lubrication system with flushing oil (light oil or oil mixed with 20% diesel), filling 60–80% of the engine’s capacity. Run the engine at idle for 3–5 minutes (do not run at high speed), then drain the flushing oil completely and add clean new oil.

Cooling System: Ensure that the cooling system of water-cooled diesel engines works well to avoid overheating. If abnormalities occur, check and eliminate them promptly.

Ventilation Device: Ensure the crankcase ventilation device works well, and regularly clean ventilation pipes and valves.

Regularly replace the oil filter to prevent dirt and impurities from entering.

Thoroughly clean the lubrication system and replace oil regularly.

Check whether water has mixed into the oil; when adding or changing oil, prevent rain, snow, or other moisture from entering.

Timely repair: when the cylinder head or engine block has cracks, the cylinder liner water ring is aged and failed, or the cylinder gasket is damaged, repair promptly. When removing the cylinder head, drain the water first to prevent water from entering the oil pan.

If the fuel injection pump supplies too much fuel, the injection pressure is too low, or the injector leaks or atomizes poorly, the diesel entering the cylinder cannot fully burn, and some will flow along the cylinder wall into the oil pan, thinning the oil, reducing viscosity, and losing lubrication too early. Therefore, regularly check or adjust the injection pump and injectors, and replace worn plungers, delivery valves, and injector nozzle assemblies in time.

When the clearance between the piston and cylinder liner, or between the valve and valve guide is too large, high-temperature and high-pressure exhaust gas will leak into the crankcase, accelerating oil aging and deterioration, forming gum, carbon deposits, and harmful acidic substances. Therefore, replace excessively worn fitting parts promptly, restore proper clearance, and maintain good sealing.

Diesel generator engine oil deterioration is a complex issue involving multiple factors. Through regular inspection, proper maintenance, using suitable engine oil, keeping the cooling system and ventilation device in good condition, preventing impurities from entering the lubrication system, and timely checking and adjusting fuel pumps and injectors, oil deterioration can be effectively prevented and controlled. This will extend the service life of diesel generators and ensure their stable operation. It is hoped that this article can provide valuable reference for the maintenance and management of diesel generators.