Are Subaru engines naturally aspirated?
Yes, Subaru engines are typically naturally aspirated, meaning they do not use forced induction like turbochargers or superchargers to increase power output. Subaru is known for its use of naturally aspirated "boxer" engines, which have a unique flat, horizontally-opposed cylinder configuration.
Subaru's Naturally Aspirated Boxer Engines
Subaru's signature engine design is the horizontally-opposed "boxer" configuration, where the pistons move in a side-to-side motion rather than the more common up-and-down motion of traditional inline or V-shaped engines. This unique layout provides several benefits, including a lower center of gravity for improved handling and balance. Subaru boxer engines are naturally aspirated, relying on the natural intake of air through the engine's intake system to generate power, rather than using forced induction.
Advantages of Naturally Aspirated Engines
There are several advantages to Subaru's use of naturally aspirated boxer engines:
- Reliability and Durability: Naturally aspirated engines tend to be more reliable and durable than turbocharged or supercharged engines, as they have fewer complex components that can potentially fail.
- Smooth Power Delivery: The flat, horizontally-opposed layout of Subaru's boxer engines provides a smooth, linear power delivery, which many drivers prefer over the more abrupt power curve of forced induction engines.
- Fuel Efficiency: Naturally aspirated engines generally have better fuel efficiency than their turbocharged counterparts, as they do not require the additional energy input to drive a turbocharger or supercharger.
- Lower Maintenance Costs: Without the added complexity of forced induction components, naturally aspirated engines typically have lower maintenance and repair costs over the long term.
While Subaru does offer turbocharged versions of some models, such as the WRX and STI, the majority of Subaru's lineup features naturally aspirated boxer engines, which have become a hallmark of the brand's engineering and performance.
What type of engine does Subaru use?
Subaru Boxer Engine
For over 45 years Subaru has been solely committed to the Subaru Boxer Engine in ALL of their models. The innovative design is part of Subaru's core DNA.
What is the most common problem with Subaru engines?
The most common Subaru engine problems are head gasket failures, particularly in older models (1997-2012 EJ series engines), which can cause coolant and oil to mix, leading to overheating. Other issues include oil leaks from the cam carriers and timing chain cover in newer engines, oil burning and consumption, and piston slap, especially on cold starts.
Head gasket failure
- What it is: A common failure in older EJ series engines where the head gasket leaks, allowing coolant and oil to mix, leading to overheating.
- Symptoms: Overheating, white smoke from the exhaust, coolant in the oil, or oil in the coolant.
- Note: This problem was more prevalent in the 1997-2012 model years and is less common in newer engines.
Oil leaks and consumption
- In newer engines: Modern F-S series engines can experience oil leaks from the cam carriers and timing chain cover, often requiring the engine to be removed for repair, notes this YouTube video.
- In older engines: Some older models, especially the 2.5L engines, are known for oil consumption between services, which can lead to engine wear if not addressed.
- Causes: Neglecting the PCV system can worsen leaks as it builds pressure inside the engine block, says this YouTube video.
Other common issues
- Engine knocking: Can occur due to a worn connecting rod bearing, which may be caused by oil starvation or other issues.
- Piston slap: A clattering noise from the engine, especially on cold starts, caused by worn tolerances between the piston and cylinder.
- Timing belt failure: In engines that use a timing belt, failure to replace it according to the manufacturer's schedule can lead to catastrophic engine damage.
Which subarus are naturally aspirated?
The 2.5L flat-four comes next with 182 horsepower under the hood of the Legacy, Outback, and Forester while available to the Crosstrek's higher trim levels. These engines are naturally aspirated, meaning air intake depends on atmospheric pressure without forced induction from a turbocharger or supercharger.
Which subarus to stay away from?
You should avoid Subaru models from specific years due to known issues, including the 2005-2009 Outback and Legacy (head gasket and oil leaks), 2010-2014 Outback and Legacy (CVT, oil consumption, windshield cracks), 2019-2022 Ascent (CVT and other engine/structural issues), and the 2012-2014 Impreza (oil consumption). Other years to approach with caution include the 2013 Crosstrek (FB20 engine models), 2015 WRX (transmission and engine problems), and several later Outback models (2017-2020) for issues like airbags, windshields, and electrical faults.
Specific Subaru models and years to avoid:
- Outback & Legacy:
- 2005-2009 Outback and Legacy: Particularly known for head gasket failures, oil leaks, catalytic converter issues, and poor interior materials.
- 2010-2014 Outback: Prone to CVT transmission failures, oil consumption from piston rings, and windshield cracking.
- 2015-2019 Outback: Some models have a risk of unintended acceleration.
- 2017-2020 Outback: Higher complaint rates related to airbags, engine failure, CVT problems, and electrical faults.
- Forester:
- 1998-2001 Forester: Known for blown head gaskets.
- 2009-2011 Forester: Affected by faulty airbags and electrical problems.
- 2014-2018 Forester: Specific FB25 engine models are associated with CVT problems.
- Ascent:
- 2019-2022 Ascent: Faced significant issues with its CVT transmission, along with other engine and structural problems.
- Impreza:
- 2012-2014 Impreza: These years often show excessive oil consumption due to faulty piston rings.
- Crosstrek:
- 2013 Crosstrek: The first model year after a redesign, it saw more complaints than later versions.
- WRX:
- 2015 WRX: Prone to transmission failures, connecting rod bearing issues, and carbon buildup in the engine.
