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Why Is My Car Burning Oil

March 3, 2024 | Victor Lukasso

If you’re experiencing higher-than-normal oil consumption in your aging vehicle, you may wonder what’s causing the problem. Burning oil is a common issue that can cause severe engine damage if ignored.

As your car ages, it’s natural to consume more engine oil. However, a few specific factors can contribute to excessive oil consumption. Worn valve stems, guides, seals, and piston rings can allow engine oil to seep into the combustion chambers.

Although this oil may burn up immediately and not produce visible smoke in the exhaust, it can still cause the oil level to decrease and affect the engine performance.

If you notice this issue, it’s essential to address it promptly to avoid further damage.


Potential Causes For Burning Oil

Understanding the causes of excessive engine oil consumption is crucial in preventing this issue. When oil enters the combustion chamber, it’s usually due to one or more worn engine components. Even newer engines that use low-viscosity oil, such as 5W-20, can experience oil consumption issues from small amounts of wear and tear.

Here are some common causes of excessive oil consumption:

1. Worn Out PCV Valve

The Positive Crankcase Ventilation (PCV) system is a critical engine component that eliminates harmful gases generated during combustion. The system achieves this by directing excess gases to the combustion chamber, where they are burned for the second time before being discharged through the exhaust.

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However, a clogged PCV system can result in oil blowback, whereby oil gets sucked into the engine through the air intake instead of removing the combustion gases. This can cause significant damage to the engine if not addressed in time.

To resolve this issue, you can replace the PCV valve. This will help restore the PCV system’s proper functioning and prevent oil blowback.

2. Worn Out Piston Rings Or Cylinder Walls

The piston rings are responsible for sealing the cylinder walls to maintain engine compression and prevent the escape of combustion gases.

However, if the piston rings are worn out, or the cylinder wall deteriorates, the seal will be compromised, and the engine oil will start entering the combustion chamber. This will result in oil burning and reduce the engine’s oil level.

3. Worn Out Valve Seal

A worn-out valve can also be a contributing factor to burning engine oil. The valve stem seals regulate oil consumption and lubrication of the valves. If these seals become damaged, they will no longer perform their intended function. Instead, they will leak oil into the engine cylinders, eventually finding their way into the combustion chamber.

4. “Normal” Oil Burning in One Vehicle May Be Excessive in Another

Manufacturers do not guide on the issue of oil burning, making it difficult for vehicle owners to determine what is expected and what is excessive.

For instance, BMW advises owners that it is normal for some engines to burn quality oil in less than a thousand miles. On the other hand, GM suggests in a tip sheet to fleet-vehicle operators that the average consumption could be about one quart within 2,000 miles for an adequately driven and maintained vehicle. Some manufacturers do not discuss oil consumption, and the answer to what is “normal” may vary depending on who is asked.

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In general, engines with less than 50,000 miles should not consume more than a quart of oil between oil changes. If your engine requires a quart of oil every 3,000 miles or less, this could indicate a leak that may not be easy to detect. Increased oil consumption should be expected as an engine surpasses 75,000 miles and 100,000 miles.

Many newer engines use thinner, lower-viscosity oils like 5W20 or 0W20 instead of 10W30. Due to their more delicate nature, they easily slip past gaskets, seals, and rings, causing them to wear out slightly over time and increase oil consumption.

What to Do When You Have a Car Burning Oil

If you see blue smoke coming from your car’s tailpipe, it indicates that your vehicle is burning oil. Oil leaking into the combustion chamber can cause many problems that need immediate attention to prevent further damage.

Even if you don’t see smoke from your exhaust, excessive oil consumption between oil changes is a sign that something is wrong with your car. A simple tune-up might be needed to fix the problem, but more extensive repairs may also be necessary.

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To address excessive oil consumption, it’s essential to regularly check your oil level and have a professional mechanic check for engine leaks, and locate the source of the oil burning. Monitoring your engine’s oil consumption over time can help you identify when it becomes excessive, alerting you to potential leaks or internal problems.

Lawsuits Due to Cars Excessively Burning Oil

Several automakers, including Audi, BMW, Honda, Subaru, and Toyota, have faced legal action due to complaints of excessive oil consumption from their customers. The issue of how much oil consumption is considered normal varies from driver to driver, leading to widespread complaints and demands for repairs from affected car owners.

To address the problem, some manufacturers have extended warranties or replaced engine parts. For instance, Honda extended the engine warranty on the 2008-11 Accords and 2010-11 CR-Vs with 4-cylinder engines to eight years/125,000 miles due to complaints from owners experiencing excessive oil consumption, which sometimes resulted in burning one quart every thousand miles.

Customers who face such problems and wish to repair their vehicles can file a complaint with their dealer or the car company.

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Meet Victor Lukasso, the owner of V. Auto Basics. Through this blog, Victor Provides Insights on the latest tips, maintenance, repair, and techniques in the automotive world.