EJ25 Engine in Phoenix, Arizona
The Subaru engine most people arrive here about, and head gasket failure is almost always the reason.
- Family
- EJ25 (EJ-series)
- Displacement
- 2.5 L
- Configuration
- Flat-four (boxer)
- Valvetrain
- SOHC or DOHC, 16 valves, depending on variant
- Produced
- 1995–2019
Bore and stroke are omitted for this family: the code covers variants with different figures, and a single pair of numbers would be wrong for some of them.
The EJ25 is the 2.5-litre member of Subaru’s long-running EJ boxer family, fitted to the Legacy and Outback from 1996 to 2019, the Forester from 1998 to 2018, and the Impreza WRX from 1999 to 2007. It exists in both naturally aspirated SOHC form, the EJ251, EJ252 and EJ253, and turbocharged DOHC form as the EJ255 and EJ257.
Head gasket failure is the reason most people arrive at this page. It is a genuinely common failure mode on the naturally aspirated EJ25, particularly on earlier builds, and it is the point at which a Subaru owner has to decide between a head gasket job and a replacement engine.
That decision is more finely balanced than it looks. A head gasket repair on a boxer engine is labour-intensive, and if the engine has overheated badly the heads may need work as well. A used replacement can be the cheaper route, but only if the replacement itself is not carrying the same latent problem, which is why the specific unit and its history matter more here than on most families.
From 2019 the EJ25 gave way to the direct-injection FB25, which is a different engine with different management and is not interchangeable.
The head gasket decision, honestly
Head gasket failure is a genuinely common outcome on the naturally aspirated EJ25, particularly on earlier builds, and it is the point at which most Subaru owners have to make a real decision rather than authorise a repair.
The decision is closer than it looks. A gasket job on a boxer engine is labour-heavy because of how the engine sits, and if the car overheated badly the heads may need machining as well. At which point the cost climbs toward a replacement engine. Get the heads assessed before choosing, because that assessment is what actually decides it.
And if you do replace: ask what has been done to the gaskets on the replacement unit, and with which parts. A used EJ25 can arrive carrying exactly the same latent problem, which is the one outcome that leaves you worse off than when you started.
Counting camshafts tells you which half you are in
The naturally aspirated variants, EJ251, EJ252, EJ253, are single-overhead-cam engines. The turbocharged EJ255 and EJ257 are twin-cam. That is the quickest structural check when a listing is vague or the paperwork is missing.
The other date that matters is 2019, when the EJ25 gave way to the FB25. The FB25 uses direct injection and different engine management; it is a different engine that shares a displacement and a boxer layout, and it is not a drop-in replacement.
Vehicles built with a EJ25
Four vehicle lines over more than two decades, split between naturally aspirated SOHC units and turbocharged DOHC ones.
| Vehicle | Years | Trim / body | Engine code | Market |
|---|---|---|---|---|
| Subaru Forester | 1998–2018 | Naturally aspirated | EJ251 / EJ253 | USDM |
| Subaru Forester XT | 2004–2013 | Turbo | EJ255 | USDM |
| Subaru Outback | 1996–2019 | : | EJ25 series | USDM |
| Subaru Legacy | 1996–2019 | : | EJ25 series | USDM |
| Subaru Impreza WRX | 2006–2014 | Turbo | EJ255 | USDM |
| Subaru Impreza WRX STI | 2004–2021 | Turbo | EJ257 | USDM |
EJ25 variants
Four codes in two groups. The naturally aspirated and turbocharged halves are not interchangeable in any respect that matters.
- EJ251 / EJ252USDM
- Earlier naturally aspirated SOHC variants.
- EJ253USDM
- Later naturally aspirated SOHC. i-AVLS variable valve lift from around 2006.
- EJ255USDM
- Turbocharged DOHC. Forester XT, Legacy GT, WRX applications.
- EJ257USDM
- Turbocharged DOHC, STI specification.
Identifying a EJ25
- Naturally aspirated EJ25 variants (EJ251, EJ252, EJ253) are SOHC; the turbocharged EJ255 and EJ257 are DOHC. Counting camshafts is the quickest structural check.
- The i-AVLS variable valve lift system appeared on the EJ253 from around 2006, which distinguishes later naturally aspirated units.
- The FB25 that replaced the EJ25 uses direct injection and is a different engine despite the similar displacement and boxer layout.
A seller describing an engine as a particular variant is making a checkable claim. Asking for a photograph of the stamp on the actual unit is not a sign of distrust; it is the normal way this gets confirmed. The engine code guide shows where each family is stamped if you want to read the one in your own car first.
What varies between EJ25 units
These are the differences that decide whether two engines with the same family code are substitutes in a particular car.
- Turbocharged and naturally aspirated variants are not interchangeable: different heads, different management, different supporting hardware.
- The FB25 is not a drop-in replacement for an EJ25.
- Ask specifically whether head gaskets have been addressed on any used naturally aspirated unit, and with what parts. This is the family where that question earns its keep.
- Timing belt driven on the EJ family: treat the belt, tensioner and water pump as part of the installation.
- All-wheel drive is standard on most applications; confirm the transmission type and whether your vehicle is manual or automatic.
Nothing on this page confirms that a specific EJ25 will work in your vehicle. That takes the year, model and trim at one end and a specific unit at the other, and it happens before a price is given rather than after. What goes into that check is set out here.
Ask about a EJ25 for your vehicle
The code is pre-filled. Add the year, model and trim, and the variant question gets settled on our side before anything is confirmed.
Common questions
Should I fix the head gaskets or replace my Subaru engine?
It depends on whether the engine overheated and what that did to the heads. A gasket job on a boxer is labour-heavy, and if the heads need machining the cost climbs quickly toward a replacement. Get the heads assessed before deciding, and if you do replace, ask what has been done to the gaskets on the replacement unit, because a used EJ25 can arrive carrying exactly the same latent problem.
Can I put an FB25 in place of my EJ25?
No. The FB25 that replaced the EJ25 from 2019 uses direct injection and different engine management. It is a different engine that happens to share a displacement and a boxer layout, and swapping one for the other is not a replacement job.
Related pages
- EJ20 EngineThe 2.0 Subaru boxer from the JDM WRX and STI.
- Subaru ForesterEJ25 head gaskets, and whether to repair or replace.
- Subaru ImprezaWRX and STI use different turbocharged engines.
- Subaru EnginesSubaru boxer engines, head gaskets, and what replacement involves.
- What Comes With a JDM EngineWhat is usually attached, what almost never is, and what to confirm in writing.
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