Why Internal Combustion Engines Burn Oil and How to Fix It


The internal combustion engine has been the heart of the automotive industry for more than a century. Despite the ongoing shift towards electric vehicles, millions of internal combustion engines still power our cars today. One common issue that plagues these engines is burning oil. In this article, we will explore why an internal combustion engine burns oil and how to fix this problem.

Causes of Oil Burning in Internal Combustion Engines

1. Worn Piston Rings

One of the primary reasons for oil burning in internal combustion engines is worn piston rings. The piston rings are crucial for maintaining proper sealing between the piston and cylinder walls. Over time, the piston rings can wear down, lose tension, or even break. This can result in gaps that allow oil to leak into the combustion chamber, where it is burned and expelled as blue smoke through the exhaust.

2. Valve Stem Seals

Valve stem seals are another component responsible for preventing oil leakage into the combustion chamber. These seals, typically made of rubber or synthetic material, prevent oil from entering the combustion chamber through the valve stems. As the seals wear down or degrade, oil can seep past them and into the combustion chamber, where it burns.

3. Worn Valve Guides

The valve guides are cylindrical components that align the valves with the combustion chamber. Over time, these guides can wear down, causing the valves to wobble and lose proper alignment. This misalignment allows oil to enter the combustion chamber through the gap between the valve stem and the valve guide, resulting in oil burning.

3. Clogged PCV System

The Positive Crankcase Ventilation (PCV) system is designed to remove harmful gases and fumes from the engine's crankcase, preventing them from contaminating the engine oil. A clogged or malfunctioning PCV system can cause pressure to build up in the crankcase, pushing oil into the combustion chamber through the piston rings or valve stem seals.

4. Overfilled Engine Oil

Overfilling the engine oil can lead to oil burning, as excess oil can be forced past the piston rings and valve stem seals. The oil level should be checked and maintained according to the manufacturer's recommendations to avoid this issue.

How to Fix Oil Burning Issues in Internal Combustion Engines

Inspect and Replace Worn Piston Rings

Inspecting the piston rings requires disassembling the engine, which can be a complex and time-consuming process. However, replacing worn or damaged piston rings can prevent further damage to the engine and solve oil burning issues. Always follow the manufacturer's guidelines for the proper procedure and replacement parts when servicing the piston rings.

Check and Replace Valve Stem Seals

To inspect the valve stem seals, the cylinder head must be removed. The seals can then be inspected for wear or damage and replaced if necessary. Like piston rings, it is crucial to follow the manufacturer's guidelines when replacing valve stem seals to ensure a proper seal.

Inspect and Replace Worn Valve Guides

When replacing valve stem seals, it's a good opportunity to inspect the valve guides for wear. If the valve guides are found to be worn, they should be replaced to restore proper alignment between the valves and the combustion chamber.

Clean or Replace the PCV System

Cleaning or replacing a clogged PCV system can alleviate oil burning issues caused by excess crankcase pressure. Regularly inspect the PCV valve and hoses for blockages and replace them as needed. Some vehicles are equipped with a PCV valve that can be cleaned with carburetor cleaner, while others require a complete replacement.

Maintain Proper Engine Oil Level

Ensure that the engine oil level is within the manufacturer's recommended range by checking it regularly. Over filling or underfilling the engine oil can lead to oil burning and other engine issues. Use the correct grade and type of engine oil as specified by the vehicle manufacturer for optimal performance and longevity.

Perform Regular Engine Maintenance

Regular engine maintenance, including timely oil changes, can help prevent oil burning issues. Over time, engine oil can become contaminated with dirt, sludge, and other particulates that can contribute to wear on internal components. Adhering to the manufacturer's recommended maintenance schedule can prolong the life of your engine and prevent oil burning.

Consider Engine Rebuilding or Replacement

In cases where extensive engine wear has occurred or multiple components are responsible for oil burning, rebuilding or replacing the engine may be the most cost-effective solution. This can be a significant investment, but it can restore the engine to like-new condition and eliminate oil burning problems. Consult with a trusted mechanic to determine if engine rebuilding or replacement is the right choice for your vehicle.


Burning oil in internal combustion engines can be caused by several factors, including worn piston rings, valve stem seals, valve guides, a clogged PCV system, and overfilled engine oil. Identifying the root cause of the problem is crucial in addressing the issue and preventing further damage to the engine.

To fix oil burning issues, regular engine maintenance and timely replacement of worn components are essential. In more severe cases, engine rebuilding or replacement may be necessary. By understanding the causes of oil burning and addressing them promptly, you can keep your internal combustion engine running smoothly and efficiently for years to come.

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