Oil analysis can prevent a crisis
Engine oil analysis can detect a number of engine operating problems. One problem which can be detected and addressed is the excess soot and unburned fuel caused by excessive idling. But just how does excessive idling produce excess soot and unburned fuel and how do these affect diesel engine operation?
A diesel engine relies on high temperatures to operate effectively. Atomised diesel fuel is sprayed into the hot, dense, compressed air in the combustion chamber and starts to vaporise and burn. A diesel engine working under load is operating at its maximum temperature, and the engine and the fuel injection system are designed to work best at these higher temperatures.
When a diesel engine is idling, it operates at lower combustion chamber temperatures. This produces an inefficient fuel burn. Lower combustion chamber temperatures lead to the production of excess soot and leave some of the fuel unburned. Both excess soot and unburned fuel have an effect on the lubricating oil and on the operation and life of the engine.
A diesel engine produces a lot of soot, so a diesel engine oil additive package contains a lot of dispersant additive. The dispersant distributes contaminants throughout the engine oil, holding them in suspension until the oil is drained and they are removed.
However, the dispersant in a diesel engine can only suspend a limited amount of soot before the soot starts to drop out of suspension and deposit on surfaces throughout the engine. Soot which deposits in the ring grooves interrupts the effective operation of the rings and engine oil starts to weep passed the rings and gets burned.
Increased oil consumption can be a sign that the engine oil needs changing. Soot can also be deposited in the engine’s oil galleries, if these become blocked then bearings will run without oil and pistons won’t get a cooling spray of oil up under their crown, bearings and pistons will seize. When the dispersant additive in the diesel engine oil becomes overloaded, the oil needs changing. The more idling, the more soot is produced, piston rings won’t operate effectively and pistons may overheat.
Unburned diesel will tend to wash the lubricating oil film from the cylinder wall. This can increase wear on both the cylinder wall and the rings, resulting in the need for earlier than planned overhaul. Unburned diesel will also dilute the engine oil throughout the engine lubrication system.
But all is not lost if for some operational reason you cannot reduce engine idling. A premium oil analysis programme can detect an increased level of soot in the oil, will highlight oil thinning and changes in the oil’s flash point because of fuel dilution, and will draw attention to increased wear metal levels.
By monitoring trends over a number of sample results, your lubricant company’s technical personnel will be able to suggest operational or maintenance changes for your diesel engines, allowing you to avoid the detrimental results of high idling operation. A shorter oil service life will probably be recommended.
But remember that an oil analysis programme will also highlight other potentially damaging conditions your engine may encounter. Coolant leaks into the engine oil, oil oxidation due to continued high temperature operation, or air cleaner failure allowing dirt to enter the engine lubrication system would all be detected with regular oil sampling and analysis. Discussing your oil analysis results with your oil supplier’s technical staff will contribute to the efficient and profitable operation of your diesel engines.
To learn more about oil analysis visit www.transdiesel.com or call Steve on 0800 848 267