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Subaru FB25 Engine - Replacement Cost, Problems & CompatibilityProblems & Compatibility
The Subaru FB25 is a 2.5-litre naturally aspirated boxer engine that replaced the EJ253 across the Forester, Legacy and Outback ranges, featuring dual AVCS variable valve timing and a timing chain rather than a belt. Reconditioned units from £2,200 - the larger-capacity FB engine found in Forester, Outback and Legacy models.
Supply & Fit Available
12-Month Warranty
Nationwide Delivery
100+ Suppliers
Used from
£1,500
Reconditioned from
£2,200
Rebuilt from
£3,500
GB
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Key Specs
Subaru FB25 - Specifications at a Glance
Engine Code
FB25 (FB25A, FB25B, FB25D)
Fuel
Petrol
Configuration
2.5L naturally aspirated flat-four (Boxer), DOHC 16-valve, open-deck aluminium block
Power Output(s)
169-175 hp (126-129 kW) pre-2018; 182 hp (136 kW) post-2018
Years Produced
2010-present
UK Models Fitted
4 models - full list in Compatibility below
2025 UK Replacement Requests
[Not in proprietary data - see compatibility demand]
Replaced
EJ253 (2.5L)
Replaced By
- (current engine; FA24 on some newer models)
Most Common Failure
Oil consumption / cam carrier leaks / cooling system
Reconditioned Price Range
£2,200-£3,500 supply-only
Vetted UK specialists for FB25 replacements
Minimum 12-month warranty on reconditioned and rebuilt options
Fitted To
Which Subaru Models Use the FB25-
The FB25 is Subaru's larger-capacity naturally aspirated boxer engine, introduced in 2010 and progressively replacing the EJ253 across the range. It is the engine of choice for Subaru's larger models where the FB20's 2.0-litre displacement would be insufficient.
| Model | Generation/Chassis | Badge(s) | Years | Link |
|---|---|---|---|---|
 Subaru Forester | SH (2010-2013) | 2.5i, 2.5X | 2010-2013 | |
| Subaru Forester | SJ (2013-2018) | 2.5i, 2.5i-L, 2.5i-S | 2013-2018 | |
| Subaru Forester | SK (2018-present) | 2.5i, 2.5i-S | 2018-present | |
| Subaru Legacy | BM/BR (2012-2014) | 2.5i | 2012-2014 | |
| Subaru Legacy | BN/BS (2014-2019) | 2.5i | 2014-2019 | |
| Subaru Outback | BR (2012-2014) | 2.5i | 2012-2014 | |
| Subaru Outback | BS (2014-present) | 2.5i | 2014-present | |
| Subaru Exiga | YA (2012-2015) | 2.5i | 2012-2015 |
02
Subaru Forester
03
Subaru Forester
04
Subaru Legacy
05
Subaru Legacy
06
Subaru Outback
07
Subaru Outback
08
Subaru Exiga
CROSS-BRAND
FB25 is documented across 8 BMW applications spanning Subaru Forester, Subaru Legacy, Subaru Outback, Subaru Exiga. Registration lookup confirms the exact suffix before quotes are sent.
Not sure which engine your car has?
Not sure which engine your car has- Enter your registration above - we'll confirm your exact FB25 fitment before any quotes are sent.
Prices
Subaru FB25 Engine Replacement Cost (UK)
Condition | Supply Only | Fitted (Independent Specialist) | Typical Warranty |
|---|---|---|---|
Used | £1,500-£2,200 | £2,300-£3,100 | 3-6 months |
Reconditioned | £2,200-£3,500 | £3,100-£4,400 | 12-24 months |
Rebuilt | £3,500-£5,000 | £4,400-£6,000 | 12-24 months |
All . Fitted = supply price + labour band below.
Labour Guide
Fitting an FB25 typically takes 10-14 hours at £65-£85/hr (independent Subaru specialist) - confirm exact labour when comparing quotes. A short block replacement on a post-2016 Subaru can cost £4,500-£5,500.
Price Factors
What genuinely moves the price for THIS engine: whether the engine is the earlier port-injection FB25A/B (2010-2018) or the later direct-injection FB25D (2018+) - the FB25D is more expensive to source and repair. Whether the engine comes from a Forester, Outback or Legacy also affects compatibility and price. See our full reconditioned engine cost guide.
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Common Problems
Subaru FB25 Engine Problems - What Actually Fails
Every engine has its weak points. Here are the known issues with the FB25, based on real-world data and verified failure patterns.
Verified issue focus: Oil consumption / cam carrier leaks / cooling system.
The FB25 improved significantly over its production run. The pre-2018 FB25A/B used port injection and was more prone to oil consumption. The 2018+ FB25D introduced direct injection, higher compression (12.0:1 vs 10.0:1) and improved power output, but oil consumption and cam carrier leaks remain concerns. Unlike the EJ25 it replaced, the FB25 does NOT have the notorious head gasket failure reputation - that issue was largely fixed with this engine generation.
Compare rebuilt FB25 prices with the failures already addressed
Engine Variants
FB25 Variants - Which One Is in Your Car-
INTRO: While FB25 is the family name, there are three primary variants - the early FB25A, the mid-production FB25B, and the later direct-injection FB25D. The differences matter when buying a replacement. ### FB25A - 2010-2012 (early port injection) - Fitted to: Subaru Forester SH (2010-2012), Subaru Legacy BM (2010-2012) - Key technical difference: Naturally aspirated, DOHC, 16-valve. Port injection. Compression ratio: 10.0:1. Power: 169 hp (126 kW) at 5,800 rpm, 235 Nm at 4,100 rpm. Dual AVCS (variable intake and exhaust valve timing). Timing chain (no belt). - Sub-code-specific failure note: Oil consumption is the primary issue on this variant - early engines are more prone to piston ring wear. - Interchange note: Direct swap with FB25B is generally possible, but check ECU compatibility. Not compatible with FB25D without significant changes. ### FB25B - 2012-2018 (port injection, revised) - Fitted to: Subaru Forester SJ (2013-2018), Subaru Legacy BN (2014-2019), Subaru Outback BS (2014-present), Subaru Exiga YA (2012-2015) - Key technical difference: Naturally aspirated, DOHC, 16-valve. Port injection. Compression ratio: 10.3:1 (increased from FB25A). Power: 173 hp (129 kW) at 5,800 rpm, 235 Nm at 4,000 rpm. Dual AVCS. - Sub-code-specific failure note: Oil consumption is less severe than FB25A but still present. Cam carrier leaks are common on higher-mileage units. - Interchange note: Generally interchangeable with FB25A, but ECU may need reflashing. Ensure the replacement matches your transmission type (CVT vs manual). ### FB25D - 2018-present (direct injection) - Fitted to: Subaru Forester SK (2018-present), Subaru Outback BT (2020-present) - Key technical difference: Naturally aspirated, DOHC, 16-valve. Direct injection (fuel injectors directly in the cylinder head). Compression ratio: 12.0:1 (significantly higher than FB25B). Power: 182 hp (136 kW) at 5,800 rpm, 247 Nm at 3,700 rpm. Dual AVCS. Features a high-pressure fuel pump. Meets Euro 6 emissions standards. - Sub-code-specific failure note: Carbon buildup on intake valves is a concern - a known downside of direct injection. Oil consumption is less common than on earlier FB25s. The higher compression ratio makes the engine more sensitive to fuel quality. - Interchange note: Not a straight swap with FB25A/B - fuel system, ECU, wiring loom, and high-pressure pump differ completely. Only replace with another FB25D. ### FB25 e-Boxer (mild hybrid) - 2020-present - Fitted to: Subaru Forester e-Boxer (some markets), Subaru Outback e-Boxer (some markets) - Key technical difference: FB25D with a mild hybrid system (12V lithium-ion battery and integrated starter-generator). The engine itself is mechanically identical to FB25D. - Sub-code-specific failure note: Same as FB25D - carbon buildup. Hybrid-specific components (battery, motor) have their own separate failure modes (not covered on this page). - Interchange note: Not a direct swap with non-hybrid FB25D without the full hybrid system.
The engine code is stamped on the top of the engine block, near the bellhousing mating face. It's also listed on the V5C registration document. For FB25D, look for the high-pressure fuel pump on the top of the engine - a clear visual indicator of direct injection. Enter your registration above if you're unsure - we'll confirm your exact FB25 variant before any quotes are sent.
Easily Confused
EJ25
- the 2.5-litre family that preceded the FB25, including EJ251, EJ253, EJ255 and EJ257. The FB25 replaced the naturally aspirated EJ251/EJ253 with a more modern design featuring dual AVCS, a timing chain, and significantly improved head gasket reliability.
Alternative / Next-Gen Code
FA24
- the 2.4-litre turbocharged boxer that is gradually replacing the FB25 in newer models (e.g., 2022+ WRX, some Outback markets). More power, direct injection, and turbocharging - but not yet widely available in the UK naturally aspirated range.
Related JLR Variants
FB20
- the 2.0-litre naturally aspirated variant of the FB family. Used in the Impreza, XV and smaller Forester models. The FB25 is essentially the same engine with larger displacement (2.5L vs 2.0L), more torque and power, but similar reliability characteristics.
Confirm the exact FB25 fitment
The engine code is stamped on the top of the engine block, near the bellhousing mating face. It's also listed on the V5C registration document. For FB25D, look for the high-pressure fuel pump on the top of the engine - a clear visual indicator of direct injection. Enter your registration above if you're unsure - we'll confirm your exact FB25 variant before any quotes are sent.
Buying Guide
Buying a Replacement FB25 - What to Choose
Choosing the right replacement route depends on your budget, risk tolerance, and ownership goals. Here's a breakdown of your options.
Used:
A used FB25 makes sense if you're replacing a high-mileage unit in a lower-value car (e.g., an early Forester or Legacy). However, be aware of oil consumption (FB25A/B) and cam carrier leaks. A used engine with documented service history and low mileage (under 60k) is a reasonable bet. Avoid early FB25A (2010-2012) with no oil consumption fix applied.
Reconditioned:
A proper FB25 recon addresses the known weak points: for FB25A/B, new piston rings with improved design (to solve oil consumption); for FB25D, a thorough carbon cleaning of intake valves. Both variants get new timing chain tensioner, new water pump, new cam carrier seals, and new gaskets. A 12-month warranty is standard. Reconditioned units are the sweet spot for most owners - you get reliability upgrades without a full rebuild.
Rebuilt:
A full FB25 rebuild is justified when you own a high-value example (e.g., a well-specced Outback or later Forester) and want the engine to last another 150,000+ miles. For FB25A/B, forged pistons can be fitted to eliminate oil consumption permanently. For FB25D, a rebuild includes new valve guides and seals to reduce carbon buildup. Budget £3,500-£5,000 for a quality rebuild.
Supply & Fit Line:
All of our vetted UK Subaru specialists offer supply-only or full supply-and-fit - nationwide delivery and recovery available, with warranties that cover both parts and labour.
Vehicle Value Note:
The FB25 sits in mid-to-large Subaru models - Forester values range from £5,000-£25,000; Outback £6,000-£28,000; Legacy £4,000-£15,000 depending on year and mileage. A reconditioned FB25 at £2,200-£3,500 represents 15-50% of vehicle value - generally viable for most examples. For a high-mileage (£4,000-£6,000) early Forester or Legacy, a full rebuild at £5,000 may approach or exceed vehicle value - evaluate the car's overall condition before committing. .
Compare FB25 Engine Prices Now --- **
Related Engines
Engines Related to the Subaru FB25
Explore engines that are closely related to the Subaru FB25, including its predecessor, successor, and key family variants.
Predecessor
EJ25
- the 2.5-litre family that preceded the FB25, including EJ251, EJ253, EJ255 and EJ257. The FB25 replaced the naturally aspirated EJ251/EJ253 with a more modern design featuring dual AVCS, a timing chain, and significantly improved head gasket reliability.
Successor
FA24
- the 2.4-litre turbocharged boxer that is gradually replacing the FB25 in newer models (e.g., 2022+ WRX, some Outback markets). More power, direct injection, and turbocharging - but not yet widely available in the UK naturally aspirated range.
Sibling
FB20
- the 2.0-litre naturally aspirated variant of the FB family. Used in the Impreza, XV and smaller Forester models. The FB25 is essentially the same engine with larger displacement (2.5L vs 2.0L), more torque and power, but similar reliability characteristics.
Sibling
FA20
- the 2.0-litre direct-injection turbo used in the Subaru BRZ / Toyota GT86 and the WRX (2015+). Not interchangeable with the FB25, but a related modern Subaru engine family.
FAQ
Subaru FB25Frequently Asked Questions
Question 1How much does a Subaru FB25 engine replacement cost-
A reconditioned FB25 supply-only costs £2,200-£3,500, with fitted prices from £3,100-£4,400. Used units start from £1,500 supply-only. Rebuilt engines cost £3,500-£5,000 supply-only.
- Used units start from £1,500 supply-only.
- Rebuilt engines cost £3,500-£5,000 supply-only.
Question 2What are the most common FB25 engine problems-
The FB25 suffers from oil consumption (FB25A/B, especially 2010-2018), cam carrier and valve cover leaks (80k-150k miles), and cooling system failures. Oil consumption can require a short block replacement or full rebuild (£2,500-£4,000). Cam carrier resealing costs £800-£1,500. Valve cover gaskets cost £300-£600. The FB25 does NOT have the EJ25's notorious head gasket failure issue.
- Oil consumption can require a short block replacement or full rebuild (£2,500-£4,000).
- Cam carrier resealing costs £800-£1,500.
- Valve cover gaskets cost £300-£600.
- The FB25 does NOT have the EJ25's notorious head gasket failure issue.
Question 3Which Subaru models use the FB25 engine-
The FB25 is fitted to the Subaru Forester (2010-present), Subaru Legacy (2012-2019), Subaru Outback (2012-present), and Subaru Exiga (2012-2015) in the UK. The FB25A/B is in pre-2018 models with port injection. The FB25D is in 2018+ models with direct injection.
- The FB25A/B is in pre-2018 models with port injection.
- The FB25D is in 2018+ models with direct injection.
Question 4Should I buy a used or reconditioned FB25-
A reconditioned FB25 is the safer choice - it includes improved piston rings (for oil consumption on FB25A/B) and new cam carrier seals, plus a 12-month warranty. Used FB25s are acceptable if low-mileage and with service history. Avoid early FB25A (2010-2012) without oil consumption fix.
- Used FB25s are acceptable if low-mileage and with service history.
- Avoid early FB25A (2010-2012) without oil consumption fix.
Question 5What's the difference between FB25 and EJ25-
The FB25 replaces the EJ25 - it has a timing chain (no belt replacement), dual AVCS, and significantly lower head gasket failure rates. The FB25 is more fuel-efficient and quieter, but early FB25A/B units suffered oil consumption issues. The FB25 is more modern but not a direct swap into an EJ25 car.
- The FB25 is more modern but not a direct swap into an EJ25 car.
Question 6How long does an FB25 engine last-
With regular maintenance (oil changes every 6k miles), an FB25 can exceed 150,000-200,000 miles. Oil consumption may appear around 60k-120k miles on earlier units. Cam carrier leaks may require attention around 80k-150k miles. The FB25 is generally more durable than the EJ25 it replaced.
- Oil consumption may appear around 60k-120k miles on earlier units.
- Cam carrier leaks may require attention around 80k-150k miles.
- The FB25 is generally more durable than the EJ25 it replaced.
Compare Subaru FB25 Engine Prices Today
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