Cummins Engine Burning Oil: Will New Piston Rings Solve the Problem?

While talking about the oil consumption issue of Cummins diesel engines, the effectiveness of replacing piston rings as a measure to overcome the issue is of great concern. In the case of a diesel engine, apart from the additional fuel consumed due to oil consumption, the issue can lead to a number of problems related to the performance of the engine. Therefore, to know whether replacing piston rings is of any great help in solving the oil consumption issue is of prime concern.

How Piston Rings Work in Cummins Diesel Engines

Piston rings are a critical component of any internal combustion engine. In Cummins diesel engines, they serve three main functions:

• Sealing the Combustion Chamber: The rings prevent high-pressure combustion gases from leaking past the piston, maintaining optimal compression.
• Controlling Engine Oil Consumption: Oil control rings scrape excess oil from the cylinder walls, preventing it from entering the combustion chamber and burning.
• Heat Transfer: Piston rings help transfer heat from the piston to the cylinder wall, protecting the piston from thermal damage.

Cummins engines, particularly in heavy vehicles, are supposed to work under high cylinder pressure and long periods of continued operations. This puts tremendous pressure on all moving parts, such as the piston rings. Hence, it becomes imperative to ensure their proper functioning, since damage to these components may even lead to leakage of combustion gases, also called blow-by, and engine oil combustion due to increased entry of lubricating oil into the burning chamber.

Common Causes of Oil Burning in Cummins Diesel Engines

The first thing to do would be to ascertain what the cause of oil burning is. Wear and tear of the piston rings could be the reason behind oil burning, but it might not be the only cause. This knowledge would help avoid replacing different engine parts unnecessarily:

• Worn or Stuck Piston Rings: Over time, the piston rings will lose their elasticity or get stuck due to carbon deposits, resulting in a decline in sealing performance and a reduction in oil scraping efficiency
• Cylindrical Wear: Out-of-round and deeply scratched cylinders cannot allow piston rings to form a proper seal.
• Valve Stem Seal Leakage: The oil will bypass the valve stem seal and enter the combustion chamber.
• Turbocharger Oil Seal Failure: A faulty oil seal may cause oil to pass into the intake system.
• Issues In Crankcase Ventilation: Excessive blow-by pressure may blow by the rings and seals.
• Poor Maintenance or Wrong Oil Type: Using incorrect viscosity of engine oil or prolonging the maintenance period will accelerate the wear of piston rings and increase the consumption of engine oil.

However, it is worth noting that replacing the piston rings by new ones may not be the only solution to the oil consumption problems. Therefore, unless the cause of the oil consumption is the replacement of the piston rings, it is imperative to note that replacing the piston rings may not be adequate to solve the oil consumption problem. Consequently, it is necessary to conduct a diagnosis of the cause of oil consumption in the diesel engine prior to replacing the piston rings with new ones. This is to be sure that there will be a solution to the problem simply through the replacement of the piston rings.

When Replacing Piston Rings CAN Fix Oil Burning

Piston rings replacement is most effective when they are the major source of oil burning. Such scenarios include:

• Gradual Increase in Oil Consumption: Early signs of wear are noted to be very slight higher oil consumption without any sudden loss of compression.
• Normal Cylinder Compression: The cylinders are usually still within specification, in which case compression tests point to worn rings.
• No Severe Cylinder Scoring or Piston Damage: Light wear and small minor glaze may be almost completely corrected by ring replacement only.

The rationale provided above on observing worn-out oil control rings and resulting in blue smoke exhaust and increased oil consumption, is very common for any fleet maintenance practice. A newly installed, properly sized Cummins piston ring can restore appropriate sealing, reduce oil consumption, and give better performance of the engine.

When Replacing Piston Rings Will NOT Solve the Problem

However, in some circumstances, even replacing the piston rings is not sufficient:

• Cylinder Liner Out-of-Round or Excess Wear: If severe, this condition prevents new rings from sealing properly.
• Deep Cylinder Scoring: Scratches or grooves on the cylinder walls affect ring performance.
• Piston Skirt Damage: Piston structural damage is never solved by rings alone.
• Long-Term Overheating or Neglect: If an engine overheats constantly, it may experience additional wear beyond the rings.

In such situations, piston rings need to be replaced with cylinder reconditioning, piston replacement, or even a complete engine overhaul. One should not simply focus on replacing piston rings. Otherwise, oil burning will persist.

Best Practices for Replacing Cummins Piston Rings

Furthermore, when replacing the piston rings, the following points should also be noted:

Pre-Replacement Inspection

• Compression Test and Blow-By Measurement: Check the compression ratio of each cylinder and measure the exhaust gas volume in the crankcase. Significant compression loss or excessive exhaust gas volume indicates piston ring wear.
• Oil Consumption Analysis: Examine the trend of the engine’s oil consumption to determine whether the oil consumption is increasing gradually or suddenly. A gradual increase usually indicates wear of the piston rings.
• Cylinder Liner Inspection: Check cylinders for any scoring, being out of round, or having steps, which might inhibit sealing.
• Endoscope Inspection: This process involves a visual inspection with the aid of a borescope to detect any buildup of carbon material.

During Replacement: Installation Practices

• Verify Ring Specifications: Ensure the rings match Cummins OEM dimensions and material requirements.
• Measure and Adjust Ring End Gap: Correct end gaps are critical for proper sealing and thermal expansion.
• Stagger Ring Gaps: Avoid aligning ring gaps to prevent blow-by paths.
• Light Cylinder Honing: If glazing exists, a light honing helps new rings seat properly.
• Proper Lubrication: Use clean engine oil to lubricate rings and cylinder walls during assembly.

Post-Replacement: Break-In and Verification

• Initial Engine Run and Leak Check: Monitor for abnormal noise, oil leaks, or compression irregularities.
• Controlled Break-In: Avoid long idle periods and full-load operation immediately. Gradually increase load to allow rings to seat.
• Monitor Oil Consumption and Exhaust Smoke: Track oil usage over the first 50–200 operating hours.
• Recheck Blow-By and Compression: Confirm that new rings are effectively sealing and restoring engine performance.

In summary, changing piston rings could solve the problem of oil consumption to some extent for Cummins diesel engines, mainly those with worn piston rings. It is therefore essential to carry out a thorough diagnosis of the condition or cause of the oil consumption before changing the piston rings. It is important to choose the correct piston ring model and specifications, as well as to follow strict operating procedures, carry out thorough adjustment and testing of the diesel engine. In addition, it is critical to enhance the maintenance of the diesel engine, improve the combustion system, and use high-tech oil control systems to comprehensively solve the oil consumption problem.