High Lube Oil Consumption In Diesel Engines
Marine diesel engines are a critical component of the shipping industry, powering cargo ships, cruise liners, and other vessels. However, high lube oil consumption can be a significant problem in marine diesel engines, leading to increased operating costs, reduced engine performance, and potential damage to the engine.
In this blog post, we will explore the causes and consequences of high lube oil consumption in marine diesel engines, as well as the steps that can be taken to prevent it. We’ll also examine the impact of high lube oil consumption on engine performance, emissions, and overall efficiency in the context of the maritime industry.
Whether you’re a marine engineer, a shipping company manager, or a boat owner, this post will provide valuable insights into the root causes of high lube oil consumption in marine diesel engines and how to address the issue to ensure optimal performance and longevity of your engine.
High Lube oil consumption
A diesel engine using the lube oil more than the specified SLOC ( specific lube oil consumption) will fall in the category of High lube oil consumption in Diesel Engines .
High lube oil consumption is generally experienced in Diesel Engines using fuel with high sulphur contents. The problem of High lube oil consumption is a severe problem, which directly affects the running cost of the engine.
Frequent addition of oil is required in the engines operating on high lube oil consumption. In the light of experience, I will discuss the topic in detail for the readers to understand and use the techniques of reducing the high oil consumption.
Reason for the High lube oil consumption
During my experience of 45 years, I have come across several engines with high lube oil consumption. Engines Oil is consumed only in the following two processes.
- If there are leakages in the lubricating oil system
- Oil burning in the engine.
Oil burning in the engine
Oil burning is a severe problem in any diesel engine. I have experienced the similar problem during my working on board ships and in Indian industries. Oil can be carried into the combustion process for the reasons listed below.
- Worn out valve guide O rings
- Worn-out valve guides increasing the running clearances.
- High lube oil temperature
- The low viscosity of oil
- Worn out piston rings
- Worn out piston ring grooves
- Worn out oil control ring
- Wrong fitment of oil control rings
- Wrong ring profiles
- Worn out piston rigs
- Worn oil scraper rings
- Excessive ovalty in Cylinder liners
- Excessive clearance in power pack
- Worn down oil control area of Piston
- Liner glazed due to the poor lubrication
- Excessive lacquer formation on the cylinder liner surface, covering the honing pattern.
Detailed reasons for lube oil burning in engine
Poor bedding of Piston rings
After the change of liners, honing of cylinder liners, and evolution of piston rings, the bedding process is carried out. During the running period, run the engine at slow speed and increase the speed in steps once engine operating parameters have settled down to normal. The machine is to be run at idle for one hour. This running period will depend on the engine type concerning the type of fuel and speed of the engine.
If the bedding process is not carried out properly, will not be established an excellent contact pattern between the cylinder liners and piston ring. Improper contact pattern will not enable to form of a satisfactory seal between the liner and rings.
Glazing of cylinder liner working surface ( High lube oil consumption in Diesel Engines)
In the new cylinder liner, the liner is glazed by the honing process. The honing process produces cross-hatching at 600 angles.
The purpose of the honing cross-hatch mark is to retain the lubricating oil for the lubrication of the Piston.
If the excess deposits of lacquers and additives used in the oil will fill these honing marks and cylinder liner will appear in the state of glazing. Glazed cylinder liners will prevent oil retention on the walls and result in the poor formation of the sealing and High lube oil consumption in Diesel Engines .
Leakages in the system– High lube oil consumption in Diesel Engines
This problem is too severe in diesel engines. Sometimes It is not easy to trace the leaking point in any diesel system. Proper tracing of the oil leakages can eliminate this problem of high lube oil consumption. Leakage of the lubricating oil may occur due to the following reasons.( High lube oil consumption in Diesel Engines)
- System oil lines
- Gaskets of the crankcase, crankcase doors, tappet covers, crankshaft seals.
- High crankcase pressure.
- Engine-driven pump gaskets
- Camshaft seals
- Timing cover gaskets
- Governor gaskets
External oil leakages major causes
- Excessive clearance in the bearings (Main and con-rod); – If the clearance in the bearing increases more than the working clearance, the oil will throw into the liners through the crankshaft. This oil throw will increase excessively in case the clearance keeps on growing. Thrown oil to the liner will travel in the combustion area and result in excessive lube oil consumption.
- Damaged camshaft bearings;- The lube oil is supplied to the camshaft bearings at pressure. If there is damage to the bearings, then the oil throw to the valves and valve guide will result in high lube oil consumption.
- Excessive taper and ovalness in the cylinder liners;- If the liners are excessively tapered and oval due to abnormal wear, Piston and piston rings will be unable to maintain the required sealing between the liners and Piston. The Piston will also have the tilting effect, and hence the oil control will not be possible. This type of abnormality will cause abnormal lube oil consumption.
- Deformed cylinder liners;- If the cylinder liner is distorted or impaired due to the abnormal thermal effect of uneven tightening with wrong torque, piston rings will not scrap the oil entirely from the distorted area of liners. Leftover oil on the cylinder walls will be burnt with the combustion process, resulting in abnormal oil consumption.
- Abrasive metal particles from honing;- if the liners are not cleaned properly after the honing process, the damage will be caused to the sealing surface due to the abrasives and impair the good sealing effect. Improper cleaning of liners will cause high lube oil consumption.
- Worn piston ring grooves;- working of the piston rings will be abnormal in the worn-out piston ring grooves. Ring groove and ring clearance will increase. The excessive clearances will cause the ring to move out of line, causing the ring to ponder. Due to the ring pondering, piston but-ends will come in the same line, and oil will be thrown to the combustion area, causing the lube oil to burn and excessive lube oil consumption.
- Excessive wear in Valves and guides.;- due to the worn-out valve spindles and valve guide, will suck in lube oil due to the vacuum created by the induction air. The sucked-in oil will be burnt and be the cause of high lube oil consumption.
- Connecting rods misaligned; – Bent connecting rod will be the main cause of connecting rod misaligned in the working axis. A misaligned connecting rod will allow the piston lading directly on the cylinder walls. This abnormal landing of the piston will not maintain the sealing effect along with the piston rings and will result in oil travel to the combustion space. If the connecting rod is misaligned, there will be abnormal clearance in the crankpin and the bearing. And will cause excessive oil throw to the combustion chamber.
- Abnormality in Piston pin;- If the piston pin is worn out and installed wrongly, it will cause oil throwing in the combustion chamber, increasing the high lube oil consumption. If the piston pin is fitted tight in the piston, it will not expand and contract the piston at changing thermal working conditions. Under such circumstances, the piston will get distorted. The distorted piston will score and scuff the liner walls and will impair the sealing effect. The impaired sealing effect will Increase the lube oil consumption.
- Clogging in the oil passages;- will block the oil passages due to carbon particles. Clogging will be more in case the engine oil is contaminated with the heavy carbon from the engine. Oil passages are meant to drain the excess oil to the crankcase. The clogged oil passages will cause the heavy accumulation of lubricating oil on top of the valve guides and the cause the oil throws to the combustion chamber. Oil passages are also used for the supply of oil to the various parts of the engine. These clogged passages will starve the lubrication of the parts and will result in damage to the parts. Damaged parts will be the reason for the high lube oil consumption.
- Uneven tightening of ant fatigue screws.;- Uneven tightening of the anti-fatigue screws of the main and connecting rods without the proper torque wrench will cause the bearing holes to get out of round. In the long run, there will be a reduction in bearing life due to the tapered holes. Increased bearing wear will cause excessive oil throw and resulting in high lube oil consumption.
- Contaminated cooling system;– Cooling water will not cool the system efficiently if the cooling system is contaminated with rust and scale, and pollutants. The rise in oil temperature increases the chances of distortion in the parts. Distorted parts will cause the oil to throw over and causes abnormal oil consumption.
- Contaminated Lube oil.;- Lube oil gets contaminated with heavy carbons due to negligence on changing oil as per the schedule. The dirty oil will clog the oil passages and cause the wear of bearings and other moving parts. Wear down in the parts will result in oil abnormalities.
- High sump oil level;- It has been observed that the sump oil level maintained high due to the wrong indication by the low lube oil alarm or inaccurate measurement of the oil level by dipstick. Indeed, a high lube oil level will cause abnormal consumption due to the connecting rod forced splashing the lube oil to the cylinder walls and the increased accumulation of oil entering the combustion chamber.
- Wrong design of piston Rings;- I have faced the problem of high lube oil consumption in one of the reputed manufacturer’s engines. My customer was having the trouble of high lube oil consumption. All the possible checks and inspections didn’t solve the problem of reducing the lube oil consumption. But nothing worked. Engine manufacturer R&D team worked continuously to eliminate the problem of high lube oil consumption. Ultimately changed the ring design with better strength. Though the lube oil consumption came down to normal, the wear rate of cylinder liners increased.
- Wrong Valve timing;- Wrong intake valve time will create the vacuum in the cylinder and suck the oil, increasing the lube oil consumption.
- High lube oil pressure: – High lube oil pressure maintained by a faulty relief valve will cause the engine to flood with oil and attribute to the high oil consumption.
- Low Lube oil Viscosity;– use of low viscous oil or the oil not matching the OEM recommendations will lead to high oil consumption.
- Lube oil diluted with fuel;- dilution of lube oil with fuel oil is the common problem in a diesel engine. May cause dilution of the lube oil due to the fuel leakage from fuel injection pumps and dripping fuel injectors. Mal functioning of the fuel valves will result in fuel mixing with lube oil and reducing the oil’s viscosity. Thin-oil with low viscosity will be the cause of abnormal lube oil consumption.
Criteria for the change of lubricating oil– High lube oil consumption in Diesel Engines
There is no thumb rule rule to determine the life of lubricating oil in an engine. Following factors will determine the life of lubricating oil.
- Fuel oil quality
- Lube oil quality
- Lubricating oil consumption
- Lube oil centrifuging efficiency
- Engine operating conditions
For the evaluation of the lube oil condition, oil is to be checked every quarterly. The sample testing period will depend upon the previous test report. Take the sample before the lube oil filter during the engine in operating condition
Guide lines for the evaluation of Lubricating oil condition
| Viscosity | Normal value [cSt @ 40° C] | min. value [cSt @ 40° C] | max. value [cSt @ 40° C] |
| SAE 30 | 100 – 105 | 75 | 160 |
| SAE 40 | 135 – 145 | 100 | 220 |
Flash Point
Flash point will indiacte the dilution
| Min. value | 185° C |
| Possible test method | ASTM D-92 |
Water Content
| Max. value | 0.2 % |
| Unit | Weight % |
| Possible test method | ASTM D4928 |
Base Number (BN)
| Min. value | The BN value should not be lower than 50% of fresh lubricating oil value, but minimum BN level never to be lower than 10-12 at operating on HFO |
| Unit | mg KOH/g |
| Possible test method | ASTM D-2896 |
Best Book On Marine Diesel Engines
Fundamentals of Medium/Heavy Duty Diesel Engines
Based on the 2014 National Automotive Technicians Education Foundation (NATEF) Medium/Heavy Truck Tasks Lists and ASE Certification Test Series for truck and bus specialists, Fundamentals of Medium/Heavy Duty Diesel Engines is designed to address these and other international training standards. The text offers comprehensive coverage of every NATEF task with clarity and precision in a concise format that ensures student comprehension and encourages critical thinking. Fundamentals of Medium/Heavy Duty Diesel Engines describes safe and effective diagnostic, repair, and maintenance procedures for today’s medium and heavy vehicle diesel engines, including the most current, relevant, and practical coverage of: • HD-OBD emission diagnostics • Common rail injection systems
Pounder’s Marine Diesel Engines and Gas Turbines
Pounder’s Marine Diesel Engines has served seagoing engineers, students of the Certificates of Competency examinations and the marine engineering industry throughout the world.
Now in its ninth edition, Pounder’s retains the directness of approach and attention to essential detail that characterized its predecessors. There are new chapters on monitoring control and HiMSEN engines as well as information on developments in electronic-controlled fuel injection. It is fully updated to cover new legislation including that on emissions and provides details on enhancing overall efficiency and cutting CO2 emissions.
After experience as a seagoing engineer with the British India Steam Navigation Company, Doug Woodyard held editorial positions with the Institution of Mechanical Engineers and the Institute of Marine Engineer
* Helps engineers to understand the latest changes to marine diesel engineers
* Careful organisation of the new edition enables readers to access the information they require
* Brand new chapters focus on monitoring control systems and HiMSEN engines.
* Over 270 high quality, clearly labelled illustrations and figures to aid understanding and help engineers quickly identify what they need to know.
A Contribution to Reduce Oil Consumption
Unlike industrialized countries, the recent rise in oil prices has had a severe negative impact on the economies of oil importing developing countries. Conventional strategies and models to reduce oil dependence, which have been implemented in the powerful “northern” economies, are often not feasible for developing countries due to high technological costs or unsuitability. Furthermore, oil reserves will deplete and consequently world market prices will climb, rather than decline over the next decade. Therefore, I propose that cross-sector strategies have to consider socio-economic circumstances of developing countries. The strategies I suggest do not rely on conventional methods such as coal, gas, nuclear or renewable energy.
Table of Marine Engineering Books
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Blog Conclusion
We hope you enjoyed our blog about High Lube Oil Consumption In Diesel Engines. Even after maintaining your engine properly, high lube oil consumption can still be a problem. This can cause your engine to run at less than optimal levels and can lead to costly repairs. This blog post can help you to understand High Lube Oil Consumption In Diesel Engines and how you can properly maintain your engine. Please let us know if you have any further questions. Thank you for reading, we are always excited when one of our posts is able to provide useful information on a topic like this!
Good Luck!!!
