Thinking about buying a Subaru or already own one? You’ve probably heard both praise and criticism about their distinctive boxer engines. These horizontally opposed engines give Subarus their unique character, but they also come with specific issues you should understand. I’ll walk you through the most common Subaru boxer engine problems, what causes them, and how to address them before they empty your wallet.
What Makes Subaru’s Boxer Engine Different?
Subaru’s boxer engine gets its name from the horizontal “punching” motion of its opposing pistons. Unlike conventional V or inline engines where pistons move up and down, boxer engine pistons move side to side in a horizontal plane.
This design creates several advantages:
- Lower center of gravity for better handling
- Naturally balanced operation with reduced vibration
- Compact design that fits efficiently in Subaru’s all-wheel-drive system
But these benefits come with their own set of challenges that have plagued various generations of Subaru vehicles.
Head Gasket Failures: The Notorious Problem
The most infamous issue with Subaru boxer engines is head gasket failure. This problem was particularly prevalent in the EJ25 2.5-liter engines manufactured between 1996 and 2004.
First Generation Issues (1996-1999)
The dual overhead cam (DOHC) EJ25 engines suffered from internal head gasket leaks that allowed coolant to enter the combustion chambers. You can identify these engines by the two humps on the valve cover.
Internal leaks are particularly dangerous because they can quickly lead to:
- Overheating
- Loss of compression
- Catastrophic engine failure if not addressed promptly
Second Generation Issues (1999-2004)
The single overhead cam (SOHC) EJ25 engines typically developed external coolant leaks. These engines have just one hump on the valve cover. While external leaks are less immediately dangerous, they still require attention to prevent overheating.
Signs of head gasket failure include:
- White exhaust smoke
- Bubbling in the coolant reservoir
- Sweet smell from the engine bay
- Milky oil deposits on the dipstick
- External coolant leaks around the engine block
Subaru recognized these problems and responded with a service campaign in 2002, adding “Genuine Cooling System Conditioner” (essentially a stop-leak product) and extending warranties to 8 years or 100,000 miles.
Oil Consumption Issues: Empty Your Oil, Empty Your Wallet
Many Subaru owners have experienced excessive oil consumption, particularly in models from 2011 to 2015. This issue became so widespread that it resulted in a significant class-action lawsuit against Subaru.
The affected vehicles included:
- 2011-2014 Forester (FB25 engine)
- 2012-2013 Impreza (FB20 engine)
- 2013 Crosstrek (FB20 engine)
- 2013 Legacy and Outback (FB25 engine)
The lawsuit alleged that defective piston rings caused engines to burn excessive oil, with some vehicles consuming up to one quart every 1,000 miles – far above what would be considered normal. Subaru eventually settled by extending warranties to 8 years/100,000 miles and providing reimbursements for oil consumption-related repairs.
If you own one of these models, you should:
- Check oil levels at least every 500 miles
- Keep records of how much oil you add between changes
- Have a consumption test performed if you suspect excessive usage
Oil Starvation: The Hidden Danger
The horizontal layout of boxer engines creates inherent oiling challenges. Unlike vertical engines where gravity helps return oil to the sump, boxer engines rely more heavily on oil pumps to circulate oil effectively.
Pickup Tube Failures
Both EJ and FA series engines suffer from oil pickup tube problems:
- EJ engines are prone to pickup tube cracking and breaking
- FA engines can experience pickup screen dislodgement
These failures can lead to immediate oil starvation and catastrophic engine damage, particularly during high-performance driving or when oil levels are low.
Prolonged Dry Starts
Modern FA and FB series engines with inverted oil filters suffer from prolonged dry starts. This occurs because oil drains from the filter during shutdown. The issue stems from oil feed and supply galleries being separated by a metal plate without proper gasket sealing, allowing air migration that defeats the anti-drain valve.
This design flaw means the engine can run without proper lubrication for several seconds during cold starts – a recipe for premature wear.
Piston Ringland Failures: The Performance Killer
Turbocharged Subaru engines, particularly the EJ25 series found in WRX and STI models, are notorious for piston ringland failures. The ringlands are the metal sections of the piston that hold the compression rings in place.
When ringlands fail, they can no longer properly seal combustion gases, resulting in:
- Loss of compression
- Power reduction
- Knocking sounds
- Potential catastrophic engine failure
Common causes include:
- Pre-ignition or detonation from poor fuel quality or improper tuning
- Prolonged hard driving without proper engine management
- Lean air-fuel mixtures causing excessive combustion temperatures
Performance enthusiasts should be particularly cautious about modifications that alter the air-fuel ratio without proper tuning.
CVT Transmission Issues: Not Technically the Engine, But Still Important
While not directly related to the boxer engine itself, Subaru’s Continuously Variable Transmission (CVT) has experienced significant reliability problems that often coincide with engine issues.
Common CVT problems include:
- Shuddering and jerking during acceleration
- High-pitched whining or droning noises
- Premature failure within 100,000 miles
- Valve body solenoid failures typically occurring around 110,000-150,000 miles
Subaru extended CVT warranties to 10 years/100,000 miles on many 2010-2018 models due to these reliability issues. However, proper maintenance with fluid changes every 30,000-40,000 miles can significantly extend CVT life, despite Subaru’s claims of “lifetime” fluid.
Modern Improvements: Has Subaru Fixed the Problems?
Subaru has made substantial improvements to address historical problems in their newer models. Modern boxer engines feature:
- Stronger head gaskets using multi-layer steel construction since the early 2010s
- Improved cooling systems with larger radiators and better heat dissipation
- Enhanced CVT designs with steel chains instead of belts and improved torque converters
- Better oiling systems in newer FA24 engines
FA24 Engine Challenges
The newer FA24 engine found in 2022+ WRX and BRZ models has its own set of issues. The primary concern involves excessive RTV (room temperature vulcanizing) sealant applied during manufacturing, which can break off and clog oil pickup screens.
This issue has been reported by numerous owners, though the severity and prevalence remain debated within the community.
Essential Maintenance Practices for Boxer Engine Longevity
To maximize your Subaru boxer engine’s reliability, follow these key maintenance practices:
- Maintain strict oil change intervals using high-quality synthetic oil
- Monitor coolant levels and address leaks promptly
- Use premium fuel in turbocharged applications to prevent detonation
- Service CVT fluid every 30,000-40,000 miles despite “lifetime” claims
- Avoid prolonged high-RPM operation when oil is cold
- Consider aftermarket oil pickup upgrades for high-performance applications
Maintenance Schedule for Maximum Reliability
| Maintenance Item | Standard Interval | Recommended Interval for Reliability |
|---|---|---|
| Oil Change | 6,000 miles | 3,000-4,000 miles |
| Coolant Flush | 30,000 miles | 24,000 miles |
| CVT Fluid | “Lifetime” | 30,000-40,000 miles |
| Timing Belt (EJ engines) | 105,000 miles | 90,000 miles |
| Spark Plugs | 60,000 miles | 30,000 miles (turbo models) |
Warning Signs You Shouldn’t Ignore
Be vigilant for these warning signs that could indicate developing problems:
- White exhaust smoke or milky oil deposits (head gasket failure)
- External coolant leaks around the engine block
- Excessive oil consumption requiring frequent top-offs
- Engine knocking or ticking especially on startup
- CVT shuddering or unusual noises
Early intervention can often prevent catastrophic failure and save thousands in repair costs.
How Reliable Are Subaru Boxer Engines Overall?
Despite these issues, Subaru boxer engines can be highly reliable when properly maintained. Many engines exceed 200,000 miles with appropriate care, and Subaru has consistently addressed major problems through design improvements and extended warranties.
For potential buyers:
- Vehicles from 2005 onwards generally avoid the worst head gasket issues
- 2020+ models represent the most refined versions of Subaru’s boxer technology
However, any used Subaru should be thoroughly inspected for signs of the common problems outlined above.
Is a Subaru Boxer Engine Right for You?
The unique character of Subaru’s boxer engine comes with both benefits and challenges. Their distinctive rumble, low center of gravity, and excellent performance in adverse conditions make them appealing to many drivers.
If you’re considering a Subaru, weigh these factors:
- Are you willing to be more vigilant about maintenance?
- Do you appreciate the unique driving dynamics enough to accept potential issues?
- Is the all-wheel-drive capability worth the trade-offs?
For many Subaru enthusiasts, the answer is yes – which explains why, despite these known issues, Subaru maintains one of the most loyal customer bases in the automotive industry.
Remember that proper maintenance and early intervention are key to avoiding the worst Subaru boxer engine problems. With the right care, these unique engines can provide hundreds of thousands of miles of reliable service.
