10 Of The Most Reliable Subaru Engines Ever Made

Japanese automaker Subaru is known for its reliability. Its vehicles have a reputation for being some of the longest-lasting in the industry, and the engines that power those vehicles need to be reliable for the Outbacks, Imprezas, and Crosstreks the company produces to stay on the road. The vast majority of Subaru vehicles are equipped with some form of the boxer engine. Porsche is the only other auto manufacturer that regularly uses the boxer, a horizontally mounted engine that features cylinders that lie flat. When the engine's pistons move past one another, it resembles the arms of sparring boxers, giving the engine its quirky name.

Subaru says the boxer engine has many benefits, including a lower center of gravity than inline or v-style engine configurations, a smaller and lighter design, and a symmetrical setup that works well with the company's all-wheel-drive systems. However, the engine's position under the hood makes for a tight fit — just ask any technicians who have had to change the side-mounted spark plugs on an Outback.

Reliability, while a subjective term, is what these engines have staked their existence on. This list of the most reliable Subaru engines aggregates model reports to determine which engines were in the brand's longest-lasting cars, and incorporates data from social media, local technicians, and respected review sites. A further explanation of the methodology can be found at the end of this article.

The 2.0-liter turbocharged boxer that powered the iconic blue-and-yellow Subaru WRX to several rally championships was a part of the EJ20 series of engines. Introduced in 1989, versions of the EJ20 were found in the Legacy, Impreza, and Outback. It's a four-cylinder boxer with an aluminum block and heads, and the engine's open deck design saved on weight, although at the sacrifice of structural support around the top of the cylinders. That's not an issue for low-powered vehicles, but as pressures and power increase, more support in the way of a semi-open or closed deck is preferred.

The EJ20 also produces the sound that many gearheads most closely associate with Subarus. That "Subie rumble" is produced by slight differences in the lengths of cylinders one and three versus those of two and four — the sound travels differently from the one pair of cylinders to the exhaust, creating a unique note.

EJ20s are generally considered to be reliable. The WRX's EJ205 is a 2.0-liter powerhouse with up to 227 horsepower and a long life expectancy if properly maintained. But if they eventually do fail, tuners and racers will often replace them with the Japanese Domestic Market (JDM) versions — either that country's EJ205s or a higher-revving Japanese exclusive EJ207. While the transition isn't as straightforward as yanking the old engine and plopping in a substitute — the Japanese engines had AVCS variable cam timing controls that the North American ones lacked — it's a doable procedure for a capable technician who knows Subarus.

[Featured image by Iamjosemom via Wikimedia Commons | Cropped and scaled | CCA 4.0 International]

This is a very touchy subject for a lot of Subaru diehards. On the one hand, it's an engine in the EJ25 lineup. Even technicians who don't specialize in Subarus know the reputation of the naturally aspirated EJ25s — they blow head gaskets, and it happened often enough to trigger multiple class-action lawsuits. However, the EJ257 is such a beloved rally powerhouse that it felt like a necessary addition to any list of Subaru engines, and there are ways to mitigate, if not solve, the issues the EJ25s present.

The EJ257 was designed specifically for the United States Domestic Market (USDM) 2004 Impreza WRX STI. It's a 2.5-liter turbocharged EJ, featuring 300 horsepower and 300 lb-ft of torque. It features a semi-closed block, meaning the tops of the cylinders are stabilized by several attaching points to the engine. There was an ultra-special version of the EJ257, tuned by Cosworth and made available to only 75 UK-only buyers. That engine was found in the Cosworth WRX STi CS400, a monster that produced 395 horsepower and 398 lb-ft of torque. Those are great specs if you can find the vehicle, but be prepared to spend a lot — recent auctions sold the 2010 vehicle for over $55,000.

While bearing and ringland issues were prevalent in early versions of the EJ257, and they never entirely went away, proper tuning and maintenance help keep the engine reliable and running in WRX STis to this day.

Replacing the EZ30 in the immediately redesigned Tribeca in 2008 (the first year of the Tribeca featured a little nose bump along the hood that was largely disliked) the EZ36 was the largest displacement engine Subaru had ever produced. In that vehicle, it produced 256 horsepower and 247 lb-ft of torque. Variable valve timing was added for both of the flat-six engine's dual overhead cams, along with changes to compression ratios, intake and exhaust manifolds, and the cooling system.

After replacing the EZ30 in the Tribeca, the EZ36 became the standard 6-cylinder engine in the Legacy and Outback as well. By the 2010 model year, the 3.6-liter engine had replaced its 3.0-liter predecessor altogether. The EZ36 is largely considered a more dependable version of the engine it replaced, with a life expectancy leaning closer to the EZ30's top end of 180k. Similar gasket leak issues to the EZ30 exist with the EZ36, and the larger engine size does tend to make repairs outside a shop environment difficult. But overall, this big six-banger delivers on performance and reliability.

[Featured image by 160SX via Wikimedia Commons | Cropped and scaled | CCA Share Alike 3.0 Unported]

Announced at the same time as its 2.0-liter baby brother, the FB25 was another redesign intended to take Subaru into the 2010s and beyond. Built off of the same aluminum cylinder block as the FB20, the FB25 also received many of the same improvements, like dual AVCS, new pistons, and two-piece aluminum heads that reduced the weight of the engine. Timing chains remained the choice over less dependable belts.

While the oil consumption issues present in the FB20 were also present with the FB25, it's important to note that those issues only affected around 5% of these engines. Although the direct fuel injection issues in FBs are common among any vehicle using that setup, it's not an issue that would affect the lifespan of the motor — a simple walnut blasting at a reputable shop cleans intake valve and port deposits and brings overall power back to spec.

As the FB20 replaced the EJ20, so the FB25 did for the EJ25s in Legacys and Foresters. It produces around 170 horsepower and 170 lb-ft of torque, and drivers say it's more responsive than the EJ25 at lower speeds. Fuel efficiency is also vastly improved over the EJ. Overall, the FB25 is considered an improvement over the AJ25 and has a lifespan of around 200,000 miles.

The FA24D, which appeared in both the 2022 Subaru BRZ and the '22 Toyota GR86, is the second collaboration between Toyota and Subaru. It addressed issues like torque dip and high oil temps. Meanwhile, the turbo version, the FA24F, debuted in the Ascent before being announced as the powerplant for the WRX, as well as being an optional upgrade for certain Legacies and Outbacks. While the FA and FB engines are still relatively new, their lifespans and reliability have already produced promising estimates.

When the FA24 was put into the WRX, it wasn't as simple as putting the same engine in a different vehicle. The version that went into the Ascent was designed for torque, with the 2019 SUV's marketing pushing its ability to tow 5,000 pounds using its 260 horsepower and 277 lb-ft of torque. When modifying the engine for the WRX, a twin-scroll turbo helped boost the engine's power to 271 horses, while torque dropped down to 258 lb-ft.

While it's difficult to judge an engine that's only been around a few years, tuners and reviewers agree that the FA24, in all its iterations, seems dependable. BRZ track drivers have discovered some issues with oil pan gasket sealant blocking the oil pickup and pressure drops on turns, but for everyday drivers, those shouldn't become concerns.

[Featured image by Chanokchon via Wikimedia Commons | Cropped and scaled | CCA Share Alike 4.0 International]