Subaru 2.5L Boxer Engine (EJ25 & FB25)
Subaru has used two completely different 2.5-litre boxer engines: the older EJ25 and the FB25 that replaced it. They are both flat-fours of the same size in the same cars, and they share almost nothing. One runs a timing belt, the other a chain. Each has its own well-known weakness. Knowing which one you have is the entire job.
Our Subaru engines start at $1,083, with market and emissions spec matched before dispatch.
Browse used Subaru engines Text your VINEJ25 or FB25? Start here
| EJ25 | FB25 | |
|---|---|---|
| Roughly | 1996–2012 | 2011 onward |
| Displacement | 2,457 cc | 2,498 cc |
| Bore × stroke | 99.5 × 79 mm (oversquare) | 94 × 90 mm (longer stroke) |
| Timing | Belt | Chain |
| Valvetrain | SOHC or DOHC depending on variant | DOHC with AVCS on intake and exhaust |
| Known for | Head gaskets | Oil consumption on early units |
The FB was a clean-sheet design. Subaru cut internal friction by around 28% with roller rockers, lighter pistons and rods and polymer-coated piston skirts, and moved to 0W-20 oil. It is about 10% more fuel efficient and holds roughly a litre more oil than the EJ, because of the chain.
EJ25: the head gasket story
This is the reputation Subaru has never quite shaken, and it is worth being precise about it rather than repeating the folklore.
The problem belongs to the EJ251, which used a single-layer coated head gasket. Failures showed up either as internal channel breaches or as external fluid leaks down the side of the block.
Subaru replaced the EJ251 with the EJ253 in most models. The EJ253 brought improved cooling, better engine management and sensors, and — the important part — multi-layer steel gaskets. That is the change that addressed it.
What this means when buying used: an EJ253 is a meaningfully different proposition from an EJ251. If you are replacing an EJ251, do not assume every 2.5 on the shelf carries the old gasket design. Ask which variant it is.
The timing belt point
EJ25 engines are interference engines — SOHC units from 1998 onward and all the DOHC ones. If the belt lets go, the valves meet the pistons. When you fit a used EJ25, fit a new belt, tensioner and idlers at the same time. The engine is out, the access is free, and the downside of not doing it is a second engine.
FB25: the oil consumption issue
The FB25 fixed the head gasket question and introduced one of its own. Subaru addressed it in service bulletin 02-157-14R, which is worth knowing by number because it defines the problem precisely.
Subaru’s threshold for a genuine fault is consumption of more than one third of a quart (10.6 fluid ounces) in 1,200 miles. Anything less is considered normal. Where the condition is confirmed, the remedy is a short block replacement, and the cause was traced to the oil control piston rings — Subaru changed their surface treatment.
Which vehicles
- 2013–14 Legacy and Outback with the 2.5 FB
- 2011–14 Forester with the 2.5 FB
- 2015 Forester with the 2.5 FB, manual transmission only
- 2012–13 Impreza and XV Crosstrek with the 2.0 FB
- 2014–15 Impreza and XV Crosstrek with the 2.0 FB, manual transmission only
The detail that matters: whether a given engine is affected comes down to VIN and engine number thresholds that vary by model, year and transmission — not to the model year alone. The engine number is the last eight characters of the number stamped on the block. That is what we check before a Subaru engine leaves here.
Subaru extended powertrain coverage for excessive oil consumption to 8 years or 100,000 miles. For most affected cars that has now lapsed, which is why these engines reach the used market.
The US vs Canada market trap
This one catches more Subaru buyers than either of the issues above, and almost nobody warns about it.
On Subarus the engine is identified by the 6th digit of the VIN. But the same model year, same model and same 2.5 litres can be a different engine depending on whether the car was built for the US or the Canadian market, and whether it is a PZEV emissions car.
You will see this on our listings written out in full, for example “2.5L, VIN A, 6th digit, US market, AT, PZEV” against “2.5L, VIN D, 6th digit, Canada market, AT, PZEV”. Same year, same car, different engine.
Send your VIN to +1 (361) 470-5276 and we will tell you the variant, the market spec and the emissions package you need. Free, and it takes minutes.
Which vehicles use the Subaru 2.5
| Engine | Vehicles and years |
|---|---|
| EJ251 | Forester 1998–2004 · Legacy and Outback 2000–2004 · Impreza 2.5RS/TS/OBS 2000–2004 · Baja 2003–2005 |
| EJ253 | Legacy and Outback 2005–2012 · Forester 2005–2010 · Impreza 2004–2011 · Baja 2005+ |
| EJ255 (turbo) | WRX 2006–2014 · Legacy GT 2005–2009 · Forester XT 2004–2013 |
| EJ257 (turbo) | WRX STI 2004–2021 |
| FB25 | Forester 2011–2018 · Legacy 2013–2019 · Outback 2013–2019 |
| FB25D (direct injection) | Forester 2019–2025 · Legacy and Outback 2020–2025 · Crosstrek 2021 onward |
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Which to buy
- EJ253 over EJ251 if the choice exists. Multi-layer steel gaskets and improved cooling are a real difference, not marketing.
- FB25 from 2015 onward avoids most of the oil consumption window, though the engine number is still the reliable check rather than the year.
- FB25D, 2019 onward, is direct injected at 12.0:1 compression and makes 182 hp. It is a different engine from the port-injected FB25 and does not simply swap into an earlier car.
- Turbo EJ255 and EJ257 are a separate conversation entirely — different internals, sodium-filled valves on the EJ255, and no interchange with the naturally aspirated engines.
Used vs remanufactured Subaru 2.5
When used makes sense
For an EJ253 or a later FB25, a good used engine is the sensible buy. Fit a new timing belt kit on any EJ while it is out and you have removed the one failure that writes these engines off.
When remanufactured makes sense
If you are replacing an EJ251 and want the gasket question closed permanently, a rebuild with multi-layer steel gaskets does that. For an FB25 with confirmed oil consumption, Subaru’s own remedy was a short block — so a rebuild with the revised rings is the equivalent fix.
Used Subaru engine prices
Our Subaru engines start at $1,083, priced by variant, market spec and mileage. Mileage on every listing is read off the donor odometer, and we photograph the actual unit before it ships.
Live prices: used Subaru engines.
What is included
Engines ship as tested assemblies. You transfer your own intake, sensors, accessories and flywheel or flexplate from the old engine. Each listing states what is attached to that unit.
On any EJ25, budget for a timing belt, tensioner and idlers. It is the cheapest insurance you will ever buy on this engine.
Shipping and warranty
Every engine is compression tested and photographed on the pallet before dispatch. Preparation takes 3 to 5 business days, then 2 to 4 days in transit on insured freight. Shipping is free to any address in all 50 states, residential included.
Standard warranty is 6 months, extendable to 3 years, with 7-day returns and free return shipping. Full terms: engine warranty policy · shipping policy · returns.
Frequently asked questions
Do all Subaru 2.5 engines blow head gaskets?
No. The problem belongs to the EJ251, which used a single-layer coated head gasket and failed either internally or as an external leak. Subaru replaced it with the EJ253, which uses multi-layer steel gaskets along with improved cooling and engine management. The FB25 that followed is a different design again.
Does the Subaru 2.5 have a timing belt or chain?
It depends which engine you have. The EJ25 uses a belt and is an interference design, so a failure damages valves. The FB25 that replaced it uses a chain. That is one of the quickest ways to tell the two apart.
Which Subarus had the oil consumption problem?
Subaru bulletin 02-157-14R covers 2013 to 2014 Legacy and Outback and 2011 to 2014 Forester with the 2.5 FB, plus 2015 Forester with a manual, and 2012 to 2013 Impreza and XV Crosstrek with the 2.0 FB, plus 2014 to 2015 with a manual. Subaru defines a genuine fault as more than a third of a quart in 1,200 miles and traced it to the oil control piston rings.
How do I know if a used FB25 has the revised piston rings?
By the engine number, not the model year. Subaru's thresholds vary by model, year and transmission, and the engine number is the last eight characters stamped on the block. Send us your VIN and we will tell you which side of the change your engine falls on.
Which VIN digit identifies a Subaru engine?
The 6th digit. But on Subaru you also need the market and emissions spec, because a US market car and a Canadian market car of the same year and model can take different engines, and PZEV cars differ again. Our listings state all three.
Will an EJ253 fit where an EJ251 was?
In many applications yes, and it is usually the better engine because of the multi-layer steel gaskets and improved cooling. Confirm by VIN first, since intake, sensors and emissions equipment vary by year and market.
Can I fit an FB25 in place of an EJ25?
No. They are different designs with different mounting, timing drive, oil capacity, management and ancillaries, despite both being 2.5-litre flat fours. Match within the family.
How much is a used Subaru 2.5 engine?
Ours start at $1,083, priced by variant, market spec and mileage. Live pricing is on the Subaru collection page, and every unit is compression tested with photos sent before dispatch.
Send your VIN and we will confirm EJ or FB, the variant, the market spec and exactly what fits.
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