The Complete Guide to Subaru Engines. (2023)

So you are interested in buying a Subaru. maybe you willstanding outin a sea of ​​similar-looking commuter cars, or maybe you just enjoy the four-wheel-drive lineup (aside from the BRZ). Either way, you've made an erudite decision. However, before buying a car, you should be aware of the most important and unique feature of Subaru - the company's engines.

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Subaru is one of only two manufacturers to use flathead engines in its cars (okay, two and a half, but we'll get to that later), and it's the only carmaker that doesn't make one.othertype of motor. Even Porsche, maker of the Boxster and flat-engined 911, uses more traditional configurations in its crossover lineup.


This makes buying a Subaru an interesting proposition for the uneducated. It's a whole new world to mechanically deal with, and many buyers get lost in forum threads, barely navigating waters full of acronyms, trying to find afour-digit mechanical quoteIt just says "head gaskets". Lucky for you, we (with the help of Subaru Engine Helpers fromIAG) are here to help: taking a look at all the Subaru engines you're likely to see for sale and how to tell if the engine you're looking for is good or bad.

The Complete Guide to Subaru Engines. (1)



A series of EJ

Found in:*Take a deep breath* 2002-2012 Subaru Impreza (including WRX and STi), 1998-2012 Subaru Legacy/Outback (including GT and XT), 2003-2006 Subaru Baja (including Turbo), 1998-2011 Subaru Forester (including XT), 2005-2006 Saab 9-2x (including Aero), 2012-2014 Subaru Impreza WRX, 2014-2021 Subaru WRX STI

When most people think of "a Subaru engine", they think of this series. The EJ series powered every Subaru from the late 90s to early 2010s with different trims, displacements, and induction methods. Imprezas, Legacies, Foresters, and even the Baja had an EJ-series engine under the hood.

Admittedly, the EJ series bikes are a bit of a hard sell in 2022. The series was first introduced in 1989 and while the upgrades it got through itsthirty two yearsof service have gone out of their way to keep it competitive; old technology can only go so far. EJs aren't exactly known for their fuel economy, high mileage, or oil retention.insidethe block, butforthe combustion chamber: what in the business world we call “where the oil has to go”.


While the EJ may not hold up to a modern-day Subaru engine, enthusiasts will probably never let the line die. The performance aftermarket for these engines isawesome, and its decades of use mean parts and information are easily accessible. Do you want to know what consequences a certain change has for your WRX? Forum posts dating back to the dotcom bubble will get your response.

The question "Should I buy an EJ-powered Subaru?" it's really a personal choice. Do you prefer modern technology and a (probably) lower mileage engine with FA or FB, or do you prefer the older platform, where every twist and mistake has been researched and documented? Are you concerned about the availability of parts for an engine that is no longer used in production vehicles, or does thirty years of after-sales support make up for what you would lose at the dealer parts counter?


With the EJ no longer being used by Subaru, the ones you see on the road (or in the Facebook marketplace) these days are reaching the age where certain service calls are required, regardless of mileage. Typically this means timing belts: every 90,000 miles or six years, a justice judge must replace the timing belt. If you're looking at a Subaru without signing up for that service, just do it. The tranquility is worth it.

EJ engines also have the most distinctive sound of the Subaru stable. That boxer sound we all know and love is due to the exhaust manifolds that come standard on these engines. The packaging limitations of this factory configuration meant that one side of the exhaust manifold was significantly longer than the other (creatively referred to as "unequal length"), and the difference in the distances the exhaust pulses travelleads to that beloved explosion.

The first USDM WRX engine: EJ205

Found in:2002-2005 Subaru Impreza WRX, 2005 Saab 9-2x Aero

In 2002, Subaru's world famous performance sedan finally arrived on American shores. The WRX was a strange little four-door (or wagon) with an inexpensive interior and a transmission that gave it all.endless warif you looked wrong However, the engine was a masterpiece for its time. You've got two liters, 227 horsepower and a lively soundtrack for your daily commute.


Twenty years later, however, the EJ205 of the first WRX has revealed some blemishes. Check for oil leaks at the rocker cover or turbocharger return line and coolant leaks at the expansion tank. The plastic and rubber hose that brings air to the turbo will dry out and crack over time, and I notice it.typeexperience that it is not fun to trade alone.

Early EJ205s had a problem with fuel lines leaking on cold starts, but Subaru issued aTechnical Service Bulletinto solve this. Be sure to get this work done before you buy an '02 or '03. Also check the condition of the crankshaft pulley, the air conditioning belt tensioner and the nest of vacuum hoses that permeate the engine compartment.


When poorly tuned or maintained, EJ205s are prone to connecting rod bearing failure. Listen for a knocking sound that varies with rpm, although it may be too low to hear at low engine speeds. If you hear this, don't buy the car or don't start negotiating the price like it's a rolling shell.

It should be noted that when these engines fail, they are usually replaced by JDM EJ205 engines. The Japanese variant had a form of variable cam timing called AVCS that was missing from US-spec cars, so be very careful if you find a WRX equipped with a new engine. Without a proper AVCS check, American cars do not come factory wired because the Japanese engine will not run properly.


The Holy Grail JDM STi Mill: EJ207

Found in:Subaru never offered it in the US, but it was often traded for WRXs and STis.


I know, I told you that this list would be a guide to the engines you are likely to encounter when buying a car. How would a Japanese-spec engine, which Subaru never sold in America, fit here? Well, Subaru engines have been known to misfire, and when they do, they leave a hole-in-the-box four-cylinder under the hood of a performance car. It has become common for owners to trade in the high-revving JDM engine of their dreams.

Most of the EJ205 problems also occur with the EJ207. Oil leaks, coolant leaks, air leaks, crankshaft pulley failure, tensioner failure, connecting rod bearing failure. Being a different JDM engine, the AVCS control issues are also worth noting.


Stay informed toothe piston is correct, as some versions of Subaru's EJ207 (particularly the V6 and V7) came with forged pistons. Forgings require different tolerances, and a forged piston will vibrate on a cold start, not to mention excessive oil consumption, caused by black gold running past the piston rings into the combustion chamber. Even so, these pistons are sought after for their robustness, which means more power can be kept in the stock engine.

The 2.5 liter that eats the head gasket: EJ25D/EJ251/EJ253/EJ259

Found in:Basismotor for Subaru Impreza 2002-2012, Subaru Legacy/Outback 1998-2012, Subaru Baja 2003-2006, Subaru Forester 1998-2011, Saab 9-2x 2005-2006


The naturally aspirated engines that have served Subaru for more than a decade. There are a few variants here, but they are all relatively minor revisions to each other. (What sets it apart is the EJ25D's double-overhead-cam design, which makes it unique among the single-overhead-cam group.)If you hear Subarus blowing head gaskets, these are the engines in question.. And before you say it, yes, the gaskets were remanufactured at the end of the engine's life, but they have still been known to fail even in the latest versions.

To detect head gasket defects, start with a real sniff. If sweet-smelling white clouds are coming out of the exhaust, you have a problem on your hands. Also check the coolant reservoir for bubbles or mixed fluids and look for signs of leaks where the block meets the heads. Note that EJ engines, while only having four cylinders, have two cylinder heads. Due to the flat layout, you have twice the chance of defects and (possibly) twice the repair costs.


In addition to head gaskets, other EJ caveats apply here. Timing belt problems, oil leaks, and connecting rod bearing failures are still common on these naturally aspirated models, though bearing problems are certainly less common here than on modified turbocharged engines.

Perhaps you are curious about the Saab mentioned above. Two glorious years, 2005 and 2006, General Motors (then owner of Saab and shareholder of Subaru) made a strange deal with the six-star manufacturer. The Subaru Impreza was renamed and sold asSaab9-2X, with the WRX appearing as the Aero version of the Saab. Commonly known as Saabarus, they are only found as pickup trucks and they are exceptionally cool.


2.5 Liter WRX Engine: EJ255

Found in:2006-2014 Subaru Impreza WRX, 2004-2013 Subaru Forester XT, 2005-2012 Subaru Legacy GT, 2005-2009 Subaru Outback XT, 2004-2006 Subaru Baja Turbo, 2006 Saab 9-2x Aero


2006 was a big year for the WRX. It got its third face in five years, replacing the 2004 and 2005 Blobeye design with the Tribeca-inspired Hawkeye front end and increasing displacement from the 2.0-litre EJ20 to the 2.5-litre EJ25. Although the new engine didn't get much peak power,Responsiveness is said to have been greatly improveddo not change.

While 2006 was a blessing for the WRX, it was actually a bit of a rough year for the EJ25 as a whole. For the past two years it had only appeared in lesser-known performance trims: the Forester, Baja, Outback, and Legacy were successful, but they weren't exactly configured as the WRX. For 2004 and 2005 that was the EJ255.essentially a detuned STi EJ257- Different heads and compression, shared with Subaru's best-performing model instead of the WRX. However, a smaller turbocharger and different intercooler prevented these cars from producing STi power.


The EJ255 has the best aftermarket support of any tuner engine, with parts available from Subaru and third-party suppliers. A great selection of ready-to-play songs from companies like Cobb make it easy to turn them into truly impressive power songs, at least for a short period of time.

In addition to the common EJ problems that two-liter engines share, the 255 brings a few new problems. Plastic intercooler end tanks have been known to separate and increase leakage (often over 18 psi on a factory turbo), and the connector between the intercooler and throttle body doesn't hold up much better. Oil filters built into the banjo bolt of the turbocharger's oil supply line have been known to clog, leaving the turbo starved of lubricant. This can cause rotors to break, metal shavings to get into the oil supply, and you trying to lift the engine just a few inches off your friend's Legacy GT at midnight in Massachusetts in December to get enough clearance above the subframe. . absorb the oil. pan. Ask me how I know.


The Complete Guide to Subaru Engines. (2)

Speaking of oil issues, watch out for cracks in the EJ255's oil pickup. replacement unitskiller bofIAGthey are a common exchange. Early Legacy GTs and Outback XTs had problems with fuel injector failures and their problemsweird side feed setupmeans they are not easily interchangeable with later model injectors.


However, the most famous problem with the EJ255 is the failure of the ground ring. The pistons themselves burst and can no longer properly hold the piston rings: compression is lost, oil enters the combustion chambers,Dogs and cats coexist. This usually happens when the engine (especially cylinder 4) is running very lean.warm, misome theorizedThat the factory exhaust manifolds that give the Boxer its rumble are partly to blame.

Remember at the beginning of Part EJ we talked about unequal length headers and the different distances that exhaust gas pulses are forced to travel before exiting the muffler? The theory is that these unequal lengths mean that the exhaust pulses from cylinders 2 and 4 arrive at the car's O2 sensor at very different temperatures than cylinders 1 and 3. The difference in exhaust pulse temperatures and densities between left and right banks -Manual cylinders force the car's ECU to make adjustments to the air-fuel ratio on a trade-off basis, which means two cylinders run good and two cylinders run poorly.


Has this already been proven? Not really, though many point to Subaru's use of equal-length heads on newer cars as proof of the theory's merits. Replacing the factory manifold on the EJ255 is considered a reliability fit on these cars, although this could just be wishful thinking.

From the USDM STi engine: EJ2

Found in:2004-2014 Subaru Impreza WRX STi, 2014-2021 Subaru WRX STI

The golden child of Subaru's American lineup. No engine makes more horsepower than the venerable EJ257, and it can be found (in various versions) in everything from the first blobeye STi to themore powerful s209. The EJ257 has unique patches from later 255s and runs with lower compression, allowing for a slightly more confident boost. In the factory version, it's mated to a bigger turbocharger than Subaru ever shipped with the EJ255.


In 2008 the engine was updated with newer cylinder heads, although the compression remained unchanged. Over the next two years, Subaru gave it a new, stronger crankshaft and updated connecting rods to match. Later revisions include theRA type block, with stronger pistons and connecting rods. since 2019all STD WRXI got the updated Type RA variant of the EJ257, something of a swan song for the bike's 15th anniversary.

The problems with the EJ255, including those carried over from other EJ series engines, are still there. But while spinning bearings and baked rings are still risks, a proper fit can help prevent them, and owners can enjoy the high levels of power that the updated internals of the modern EJ257 can handle.


The Complete Guide to Subaru Engines. (3)

from EZ-series

Found in:Subaru Tribeca (all vehicles), Subaru Legacy 3.0R/3.6R 2008-2019, Subaru Outback 2000-2019 3.0R/3.6R


Subaru may be best known for its four-cylinder engines, but don't fall asleep on the EZ-series six-cylinder engines. One formed the basis for the famousPowerful Car Mods Build Supergramps, where it was combined with the E85 and a custom turbo kit had to be mademore than 400 hpon wheels.

The EZ engines, available in 3.0-liter and 3.6-liter versions, are known for being reliable if somewhat disappointing engines. They get rid of the troublesome EJ timing belt for a timing chain, and their naturally aspirated means no trouble with leaking turbos, intercoolers or air intakes. Some oil leaks at the valve covers and timing chain are to be expected, but they shouldn't coincide with leaks from the "valve cover gasket which drips oil directly into the manifolds, so The car starts to smoke at a red light." Voice of experience on this.


If EZ motors have a fatal flaw, it's the difficulty of accessing some components. The water pump is located behind the hood, making replacement a time-consuming (and expensive, hour-long) mechanical job. The EZs also have problems with their serpentine belt bearings. If there is noise, vibration or wobble in the pulleys, estimate the cost of replacing them.

The Complete Guide to Subaru Engines. (4)


from the FB series

Found in:2012+ Subaru Impreza, 2012+ Subaru XV/Crosstrek, 2011+ Subaru Forester, 2013+ Subaru Legacy, 2013+ Subaru Outback


EJ and EZ engines, as beloved as they are, are not built to last forever. Modern innovations in engine design, injection systems and emissions equipment eventually forced them to step aside. Their replacements, the FA and FB series engines, are so new that some mechanical failures are still unknown, but many have already surfaced.

We'll cover the FB-series engines first, as they're the most standard fare for touring. FA engines will follow, including the now standard turbocharged FA24F which replaces the EJ255, EJ257 and EZ engines. Save the best for last, right?


The modern 2.0-litre commuter: FB20

Found in:2012+ Subaru Impreza, 2012+ Subaru XV/Crosstrek

Subaru has made a number of minor revisions to the FB20 engine over the years, none of which were surprising. These are the first Subaru Suburban engines to be useddirect injection, where the fuel is injected directly into the cylinder instead of in front of the intake valves. While this has its benefits in terms of efficiency, it can leave the backs of the valves covered in carbon that a more standard port injection system would self-clean. This is not unique to Subaru, however, and carries the same risks as any other modern direct-injection engine.


Like all flat engines that are not made in Stuttgart, FB20 engines often have small oil leaks. However, a major lubrication problem is theTSB oil consumptionwhich Subaru released for both FB engines. Despite the result of aclass action lawsuitThe problem is said to affect a small percentage of cars. Still, it's worth checking an ad's VIN against the TSB before you sign the title.

The FB series is also included.threeHybrid variants: FB20X, FB20V and FB20D e-Boxer. None of them is a revolution compared to their ICE counterparts, and only the FB20V is still in production. It's limited to one model, the Crosstrek Hybrid, and gets most electrical parts from Toyota. Aspect...principal.


While FB engines are largely reliable, the CVT transmissions they're mated to are often a source of trouble. Subaru has been having some CVT issues latelyExtended warranty on some address the problems. If you're going to buy a modern Subaru, consider the manual transmission. If you're interested in this bike, probably not, but I can dream.

The modern 2.5-litre commuter: FB25

Found in:2011+ Subaru Forester, 2013+ Subaru Legacy, 2013+ Subaru Outback, 2021+ Subaru Crosstrek (uitrustingsniveaus Sport y Limited)


If you want something that feels faster than the FB20, but is virtually identical overall, the FB25 is your choice. No turbo yet, but the FB25 adds a bit of displacement, which, while replaceable, is still nice. The FB25 is offered primarily in heavier Subaru vehicles, so there's no 2.5-liter Impreza on the menu.

Problems with the FB25 are transmitted from the FB20. Small oil leaks, TSB oil consumption, but most of the problems are CVT related. When it comes to Subaru's modern transportation offerings, a traditional Toyota or Honda inline design is probably more reliable, but in modern carsinIs trustworthy. At least in Subaru it is also interesting and has all-wheel drive as standard.


The Complete Guide to Subaru Engines. (5)

From FA-series

Found in:2012+ Subaru BRZ, 2012-2016 Scion FR-S, 2016-2020 Toyota 86, 2015-2021 Subaru WRX, 2014-2018 Forester XT, 2022+ Toyota GR86, 2018+ Subaru Ascent, 2020+ Subaru Legacy Xt, 2020+ Subaru Outback XT, 2022+ Subaru WRX


Subaru's FB engines are great commuter vehicles, but they can't compete in the performance market. For this, the emblem of the six stars offers another range of engines: the FA series. FA engines do notexclusivelyfor performance use, but all the performance engines Subaru makes are from the FA range.

The first Toyobaru engine: FA20D

Found in:2012-2020 Subaru BRZ, 2012-2016 Scion FR-S, 2016-2020 Toyota 86

Do you remember where I said two?and some halvesDo car manufacturers use boxer engines? We have already played in Saab, but Scion (RIP) and Toyota also count. The FA20D, shared with the FR-S and 86, is unique among Subaru engines in that it also exists under another name: Toyota 4U-GSE. Toyota participated in the development of the FA20D by borrowing its direct injection system and D-4S port, and for this contribution the company earned the right to revive the name of the flat U-series engine it used in the left-hand years. seventy.


The FA20D is known for its torque drop, the complete loss of any throttle feel in the mid-rev range, you know, where your bike spends most of its time off-road. This can be fixed by headbutting or by judiciously applying forced induction. However, the latter will power one of the FA20Ds.otherDiabolical.

Regardless of the chassis or grill shape, the FA20D gets hot. These engines burn coil packs and dilute the oil like it's their job. It's gotten to the point where an oil cooler is almost seen on forums as a must-have trackday accessory. The loss of oil pressure that occurs at high temperatures and high RPM in these engines has been known to cause misfiring on the track, so add a few weights of oil before your next HPDE. Superchargers and (especially) turbochargers compound the problem, so give the next BRZ you see with a vented hood a break. It could also be functional.


The 2012 and 2013 FA20D engines were recalled due to valve train issues, to replace the valve springs. However, for many cars the cure turned out to be worse than the disease. Reports of engines failing mere hundreds of miles after the repair poured in, and the problems were mostly centered on the Scion side. The leading theory, supported by some bad engine teardowns, is that Scion dealership technicians simply weren't used to applying sealant to the boxer's unique design. Too much sealant was applied during engine reassembly, causing it to enter the crankcase and clog the truck. If you plan to buy one of these cars, avoid the 2012 and 2013 models if possible.

At high revs, these engines are also at risk of losing their rocker arms. When turned all the way to redline, the rocker arms can dislodge from their location in the valve train, and in the worst case come out through the valve cover.


The return of the 2.0-liter WRX engine: FA20F

Found in:2015-2021 Subaru WRX, 2014-2018 Forestal XT

Ah, the FA20F. The engine that's powered the less-beloved-but-best-selling generation of the WRX since last, at least until Subaru last year introduced an even less-beloved generation that's likely to sell even better. The FA20F returned the WRX to its two-liter roots, but introduced direct injection to the party.


These engines are largely reliable when worn out, but can fail if tuners try to add too much power. The weak point of the FA20F is the connecting rods, which can become loose when drivers demand a lot of push at low revs. This request may be harmfulelkmodern turbo engine so remember to hit the gas instead of throttle when stopped. Your cranks will thank you.

Like other direct injection turbocharged engines, the FA20F can fall victimlow speed ignition advance. If you've ever wondered why so many cars now require a 91 octane rating, high octane is a preventative measure against LSPI. Motor oil formulas are also said to have an effect, so don't give your WRX cheap stuff.


Interestingly, aftermarket exhausts have been known to make this generation of WRX spew smoke. The problem comes from the turbocharger itself: lower exhaust back pressure means less force is exerted on the turbo oil seals, which can cause some of it to leak into the exhaust. The solution is aturbocarterbegrenzer, which helps to evacuate the oil from the turbo before the pressure builds up.

The second Toyobaru engine: FA24D

Found in:2022+ Subaru BRZ, 2022+ Toyota GR86

The FA24D made its debut in the updated 2022 BRZ and GR86. It retains Toyota's D-4S injection system from the FA20D, but has increased the smaller engine's famous 86mm bore to 94mm. It is said to eliminate old engine torque droop, or at least mitigate its worst effects.


The FA24D has also addressed one of the major shortcomings of the FA20D.adding a factory oil cooler. While not a true liquid-to-air cooler, instead of cooling the oil with coolant from the engine block, it should help bring the oil temps down from their peaks more quickly, even if it doesn't do much to keep them under load.

Now that the FA24D is just beginning to find its way into the hands of owners, not much is known about its reliability. However, given the amount of technology shared with the FA20, expect many of the same caveats to apply.


The modern turbomill: FA24F

Found in:2018+ Subaru Ascent, 2020+ Subaru Legacy XT, 2020+ Subaru Outback XT, 2022+ Subaru WRX


Here it is, Subaru's modern golden son. Gone are the EJ207 and 257, the FA20F and the EJ255. This is the new Subaru turbocharged engine,singular. While the company has yet to confirm the engine's use in an updated STI, it is suggested that it is now just the Subaru Turbo engine. Expect dynamics more akin to the EJ255/EJ257 split than anything overly dramatic.

The FA24F made its first appearance on the Ascent, leading many to deride it as "just a cross bike" when it was announced for the WRX. The downside, however, is that those years on the Ascent served as a proving ground; it is now ready for performance applications.


Like the FA24D, the FA24F is too new to have a definitive list of common problems and their solutions. However, expect them to appear in the hands of thousands of tuners with more money than common sense in the next few years. This is the true test of an engine's reliability: how well it stands up to the whims of an indifferent owner.

Should you buy a boxer?

Ultimately, it's up to you. Subaru's flat-four and six-cylinder engines are known for their low center of gravity, extensive aftermarket support, andFantasticsound. The relatively large displacement, turbocharged four-cylinder (except for the FA20F) has seriously exhilarating powerbands that can make you feel like Colin McRae in any snowy parking lot. Trust me, having owned two, I understand the appeal.


But I also get folders full of maintenance receipts, the trial and error of finding a store that really understands unique design, and emails from my credit card company saying, "Hey, were you thinking about spending that much? Spend on parts and labor. ?" The benefits of a boxer engine are not free, and there are reasons why Subaru is the only manufacturer to use this design exclusively. Boxers are heavier, mechanically more complex, and more difficult to drive than a traditional inline engine. Work doing it yourself requires a lot of unique knowledge, and taking one to a repair shop means doing some research to find a mechanic who doesn't fill the oil passages with sealant.

Like all engine designs, Subaru's boxers have advantages and disadvantages. Hopefully, after reading the last 4,500 words, you'll have an idea of ​​what they are, and whether your own yellow notebook of factors is moving more toward the positive or the negative.


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