Why do subarus use so much oil?

Subaru vehicles are known for their reliable performance and all-wheel-drive capabilities, but one common issue that many Subaru owners face is excessive oil consumption. This can be a frustrating problem, as it requires frequent oil top-ups and can be a sign of a more serious underlying issue. In this article, we'll explore the reasons why Subarus tend to use more oil than other car models.

Causes of Excessive Oil Consumption in Subarus

There are several factors that can contribute to the high oil consumption in Subaru vehicles:

• Boxer Engine Design - Subarus are equipped with a unique "boxer" engine design, where the cylinders are horizontally opposed. This layout can lead to increased oil consumption due to the engine's complex internal structure and the way the pistons move.


• Piston Ring Design - The piston rings in Subaru engines are designed to be thinner and more flexible, which can allow more oil to pass through and be burned during combustion. This is a trade-off for improved fuel efficiency and performance.li>
  
• Turbochargers - Many Subaru models, especially the performance-oriented variants, come equipped with turbochargers. Turbochargers can increase oil consumption by allowing more oil to be drawn into the engine during high-speed operation.


• Mileage and Age - As Subaru engines accumulate more miles, the piston rings and other components can wear down, leading to increased oil consumption over time. Older Subaru models tend to have higher oil consumption rates.li>
  

It's important to note that while high oil consumption is a common issue with Subarus, the severity can vary depending on the specific model, engine, and driving conditions. Regular maintenance and monitoring of oil levels can help mitigate the problem.

Addressing Excessive Oil Consumption

If you own a Subaru and are experiencing excessive oil consumption, there are a few steps you can take to address the issue:

• Check Oil Levels Regularly - Make a habit of checking your oil level at least once a month, or more frequently if you notice the level dropping quickly. Top up the oil as needed to maintain the proper level.li>
  
• Use the Recommended Oil Type - Consult your owner's manual and use the oil type and viscosity recommended by Subaru. Using the wrong oil can exacerbate oil consumption issues.


• Consider an Oil Consumption Test - If the oil consumption is severe, your Subaru dealer may be able to perform an oil consumption test to determine the root cause and recommend appropriate repairs.


• Seek Professional Assistance - In some cases, excessive oil consumption may require more extensive repairs, such as replacing piston rings or other engine components. It's best to have a qualified Subaru technician diagnose and address the problem.li>
  

By understanding the reasons behind Subaru's tendency for high oil consumption and taking proactive steps to monitor and address the issue, you can help maintain the health and performance of your Subaru vehicle.

Why is my oil disappearing but no leak?

Losing oil with no visible leak is most likely due to the engine burning the oil internally. This can happen when worn components like piston rings or valve seals allow oil to slip into the combustion chamber, where it's burned off. Other causes can include a faulty PCV valve or a blown head gasket. You should have a mechanic inspect your car to prevent severe engine damage. 
This video explains the common causes of an engine burning oil: 59sHonest Mechanic ColoradoYouTube · May 22, 2024
Common causes of internal oil loss

• Worn piston rings: The rings create a seal between the piston and cylinder wall. As they wear down, oil can slip past them and burn in the combustion chamber. 
• Worn valve seals: These seals prevent oil from leaking down the valve stems. If they fail, oil can enter the combustion chamber. 
• Faulty PCV valve: The positive crankcase ventilation (PCV) system removes pressure from the crankcase. If the PCV valve is clogged, it can cause pressure buildup and force oil into other parts of the engine, leading it to be burned. 
• Blown head gasket: A damaged head gasket can allow oil to leak from the engine's oil passages into the combustion chambers. 
• Engine wear: Over time, general engine wear can lead to more oil being consumed during normal operation. 

You can watch this video to see how a faulty PCV valve can lead to oil burning: 1mScotty KilmerYouTube · Oct 7, 2014
What to do next

• Check for blue smoke: While you may not see an external leak, burning oil can often produce a blue or grayish smoke from the exhaust, especially when the engine is under load or after idling. However, if the oil loss is gradual, the smoke might not be noticeable. 
• Consult a mechanic: It is best to have a professional diagnose the problem. They can perform tests like a compression or leak-down test to pinpoint the source of the oil loss. 
• Address the issue promptly: Ignoring oil loss can lead to significant engine damage and costly repairs. Getting the problem fixed early is crucial for your car's longevity. 

Why does my Subaru burn oil so fast?

Your Subaru may burn oil fast due to engine wear, such as worn piston rings and valve seals, which allows oil to enter the combustion chamber. Other causes include a faulty PCV system, carbon buildup from using low-quality fuel, or using a thin synthetic oil in an engine with looser tolerances. Addressing these issues can help, and for many Subaru owners, frequent oil checks and using a slightly heavier synthetic oil can reduce consumption. 
Common causes

• Worn piston rings or valve seals: Over time, these parts can wear out, allowing oil to leak past the pistons or through the valve guides and into the combustion chamber where it's burned. 
• Malfunctioning PCV system: A clogged or broken Positive Crankcase Ventilation (PCV) valve can lead to pressure buildup, forcing oil out of the engine. 
• Carbon buildup: Low-quality fuel can lead to carbon deposits that can cause piston rings to stick, allowing oil to seep into the combustion chamber. 
• Engine design and oil type: Modern engines with looser tolerances, in combination with thin synthetic oils, can be more prone to oil consumption. 
• Turbocharger wear: On turbocharged models, worn turbocharger components can lead to oil leaks into the intake or exhaust systems. 

What you can do

• Check your oil level regularly: It's recommended to check your oil level every few gas fill-ups and to top it off as needed to prevent the engine from running low. 
• Use high-quality oil: Using a high-quality synthetic oil can help. Some owners report reduced consumption by switching to a slightly heavier weight, like from a 0W−200 cap W minus 200𝑊−20 to a 5W−305 cap W minus 305𝑊−30 synthetic oil, though this may slightly decrease fuel economy. 
• Ensure regular maintenance: Follow the manufacturer's recommended oil change intervals and use the correct oil grade. 
• Inspect the PCV valve: A malfunctioning PCV valve is an inexpensive fix that may reduce oil consumption. 
• Get a professional diagnosis: If the problem persists, have a mechanic inspect the engine for worn components like piston rings or valve seals. They can also perform a compression test to assess engine wear. 
• Consider an Air-Oil Separator (AOS): Installing an AOS can help reduce oil consumption in many Subaru engines. 

What is the most common issue with Subaru?

The most common Subaru problems include issues with head gaskets, oil consumption, and transmission problems, particularly with older EJ engines and certain first-generation CVTs. Other frequent issues involve timing belt failures, electrical faults, and suspension wear. Many of these issues are more prevalent in specific older model years, though newer models can still experience problems like transmission wear.
 
This video discusses common issues with Subaru engines and transmissions: 58sThe OCD RepairmanYouTube · Jul 7, 2025
Engine and powertrain problems 

• Head gasket leaks: This is a notorious issue, especially in older models with EJ series engines, and can lead to coolant leaks, overheating, and other engine damage. 
• Engine oil consumption: Some models consume excessive oil, often due to worn piston rings or valve seals. 
• Timing belt failures: A failing timing belt can cause severe engine damage, and replacement should be done according to the manufacturer's schedule. 
• Transmission problems: Issues like slipping gears or rough shifting have been reported, particularly in some first-generation Lineartronic CVTs and certain models with higher torque loads. 

Other common issues

• Electrical issues: Various components can have faults, including sensors, alternators, and starters. 
• Suspension problems: Suspension components can wear out over time, leading to excessive noise, vibration, and poor handling. 
• Defective airbags: Some model years have had issues with airbags. 
• Faulty fuel pumps: Problems with fuel pumps have been reported in some models. 
• Weak windshields: Some owners have complained about the durability of the windshields. 

Tips to mitigate problems

• Perform regular maintenance: Consistent oil changes, fluid checks, and other scheduled maintenance can help prevent many issues and extend engine life. 
• Replace the timing belt on schedule: Adhering to the manufacturer's recommended timing belt replacement interval is crucial to avoid catastrophic engine damage. 
• Be mindful of specific model years: Researching specific model years for known problems can help you make a more informed decision, especially when buying used. 

Do Subarus go through a lot of oil?

The issue is the opposite of rare. Every single Subaru does it. It is not a design flaw. Due to the engine layout, it inherently burns oil. Most will burn about 1 quart every 3000 miles. Some more than others. Some burn very little. But they all burn oil.