4 Common Problems With Subaru Boxer Engine

Throughout the history of the automobile, hundreds of engine configurations have come and gone. But only a few have captured the imagination of car enthusiasts, like the Subaru Boxer. This legendary engine has found its way under the hood of many Subarus throughout the years and is one of the most desirable engines to come out of Japan.

But, when it comes to the Subaru Boxer, not everything is sunshine and roses. There are a few notable reliability issues with this powerplant. In this article, we’ll tell talk about everything you need to know about them.

Head gasket issues, PCV problems, excessive oil consumption, and engine oil starvation are some of the most common Subaru Boxer engine problems. Keep these issues in mind the next time you are on the hunt for a cool JDM ride with a “cluster of stars” as its logo.

History of the Subaru Boxer

Subaru Boxer Engine

We thought it would be useful to give you a historical overview of the Subaru Boxer engine before discussing its common failure points.

Boxer engines – also referred to by some as flat engines have a history that runs back to the 19th century. Karl Benz, the inventor of the first motor cars used boxer engines to power his race cars. The 1933 Porsche Type 32 also used a flat-four, as did the ever-popular Volkswagen Beetle.

Subaru was another early adopter of the Boxer engine. The 1966 Subaru 1000 holds the accolade of being the first production car from the Japanese car maker to come with a Boxer engine under the hood. It had a tiny 10-liter engine, which produced 55 hp to help this commuter car stroll down the highway.

Although the popularity of this engine design has gone down in recent years, both Porsche and Subaru are keeping this iconic engine design alive as of 2023.

How Does A Boxer Engine Work?

Now that you know the history of this unique engine configuration, let us look into how it works.

Undoubtedly, the main feature that sets Boxer engines apart from the rest is their unique layout. Here, the cylinders are arranged horizontally at a 180-degree angle from each other. This gives the impression that the pistons are “jabbing like boxers” at each other.

Boxer engines usually have four or six cylinders, and their displacement varies depending on the application. Subaru adds turbochargers to some of their Boxer engines to give them a healthy increase in horsepower.

Boxer Engine Pros and Cons

Subaru Métropolitain | Subaru Boxer Engine

With that out of the way, you may be curious to learn the benefits and drawbacks of Boxer engines compared to other designs. If so, you’re in luck!

Let’s start things off by taking a look at the pros of having a Boxer engine under the hood of your Subaru.

  • Lower Center of Gravity
  • Improved Safety
  • Balance
  • Ride Comfort

Lower Center of Gravity

The unique design of Boxer engines allows vehicle manufacturers to place them lower inside the engine bay. This allows the overall ride height to be lower, improving vehicle stability and agility.

You’ll especially feel the added advantages of the lower center of gravity when taking corners at high speed in your Boxer-equipped Subaru. Additionally, the lower center of gravity keeps your ride planted on the road at all times.

Improved Safety

Having a flat engine positively contributes toward your safety out on public roads too. As it is positioned lower than normal engines, the risk of the engine intruding into the passenger compartment during a head-on collision significantly decreases.


Another huge benefit of the Boxer engine design is improving the overall balance and handling characteristics of your Subaru. In these engines, the two cylinder banks sit on opposite sides, sandwiching the crankshaft in the middle.

As the engine lies along the center line of the car, its weight is equally distributed to either side of the vehicle. You’ll feel the impact of the improved engine balance the most when changing directions rapidly.

Ride Comfort

This ties into the previous point, as the improved engine balance contributes towards increasing ride comfort. By nature, internal combustion engines make a lot of noise and vibrations when they are running.

However, the horizontal positioning of the pistons inside a Boxer engine cancels out some of these excessive noises and vibrations, allowing passengers to have a comfortable ride.

As we mentioned earlier, the Boxer engine design has a few negatives too. Due to the compact nature of these powerplants, they are notoriously hard to work on. As a result, you’ll have to spend significantly more time and money if something goes wrong under the hood of your Subaru.

The unique nature of this engine configuration also takes a toll on efficiency. Inline and “V” shaped engines are generally more efficient than Boxers, mainly due to differences in bore sizes. It is important to note that these efficiency issues have been addressed with modern iterations of the Boxer engine.

Now that we have the basics out of the way, it is time for us to focus on the reliability issues Subaru Boxer engine owners have to endure.

Most Common Subaru Boxer Engine Problems

Here are the engine issues every Subaru Boxer engine lover should know about.

  1. Head Gasket Issues
  2. Excessive Oil Consumption
  3. Engine Oil Starvation
  4. PCV Problems

How exactly do these issues wreak havoc on Boxer engines? Let’s find out!

Head Gasket Issues

When talking about Subaru Boxer engine issues, the head gasket is the perfect place to start. Wondering why? Well, when looking into the history of this engine, it seems that each iteration of it has some form of head gasket-related problem.

Head gasket issues started to rear their head with the 1st generation 2.5-liter Boxer engines produced between 1996 and 1999. The problems later returned with the EJ251, EJ252, and EJ253 variants.

On both occasions, leaks in the head gasket allowed coolant and engine oil to leak between the head and the engine block due to a construction defect. You see, the head gaskets in question had a single-layer graphite coating. Once the engine passed the 100,000-mile mark, this coating would strip away, weakening the head gasket seal.

Modern Subaru Boxer engines have remedied this issue by using a non-coated multilayer head gasket.

Excessive Oil Consumption

Excessive oil consumption is another issue that plagues Boxer engines made by Subaru. This problem was prominent in models made between 2011 to 2015 including the Forester, Legacy, Impreza, and Outback. Oh, and did we mention that this issue even caused a class-action lawsuit?

On most occasions, the increase in oil consumption was caused by oil control ring failures in the engine. Over time, burning excessive amounts of oil can even cause catastrophic engine failures.

Engine Oil Starvation

Next, let’s shift our attention from one oil-related Subaru Boxer engine problem to another. Oil starvation inside the engine can cause a whole host of expensive problems, like crankshaft bearing failures, scratches on the cylinder walls, and engine seizures.

PCV Problems

The Positive Crankcase Ventilation valve is an important component in a Subaru’s emissions system. It has several responsibilities, including keeping the engine clean, preventing pressure buildup in the crankcase, and preventing toxic pollutants from being released into the environment.

However, if you notice blue or gray smoke escaping from the tailpipe, there is a high chance that this component has gone bad. When the PCV valve goes bad, the vehicle would lose performance as you are driving.

Subaru issued a recall to rectify PCV-related problems in 2019, where they replaced the part in over 250,000 Imprezam Crosstrek and Forester models.

Preventive Maintenance Tips To Limit Subaru Boxer Engine Problems

There are several maintenance procedures you can follow to prolong the life of your beloved Subaru’s Boxer engine.

  • Monitor Oil Levels
  • Keep An Eye On Fluid Levels
  • Change the Air Filter

Monitor Oil Levels

We mentioned several engine oil-related issues in this article. The best way to prevent these problems is to keep an eye on the engine oil levels. Engine oil is essential for keeping the internals lubricated so that they don’t rub against each other and create friction.

Make sure to take a dipstick reading once every couple of weeks. In addition to the oil level, pay attention to the quality of the oil as well. Ideally, you should replace conventional engine oil every 3000 miles, or synthetic oil every 7500 to 15,000 miles.

Keep An Eye On Fluid Levels

Similar to engine oil, other fluids such as coolant, brake fluid, and gear oil are essential for the functionality of a Boxer engine as well. Ensure that the fluid levels remain above the minimum mark at all times.

Change the Air Filter

The air filter is another component that needs to be replaced over time. It keeps dirt and debris from entering through the air intake and interfering with the combustion process. It is a good rule of thumb to replace the air filter every 12,000 to 15,000 miles.

If you own a Subaru with a Boxer engine or are in the market for one, make sure to keep an eye out for these problems. If you carry out regular maintenance and follow the tips we provided, a Boxer engine will serve you reliably for years to come.

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Mahir Ahmed


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