The SUBARU FB24 is a 2,387 cc, flat — four petrol engine produced between 2019 and 2025. It features DOHC, 16 — valve configuration with direct fuel injection and naturally aspirated aspiration. Rated at 137 kW (186 PS) and 235 Nm of torque, this engine was developed for balanced performance in all — wheel — drive sedans, wagons, and SUVs.
Fitted to select North American and global — market Subarus including the Outback and Legacy, the FB24 was engineered for responsive drivin…
Production years 2019–2025 meet U.S. Tier 2 Bin 5 and EPA Tier 3 standards depending on market (VCA UK Type Approval #VCA/EMS/FB24).
The SUBARU FB24 is a 2,387 cc flat-four naturally aspirated petrol engine engineered for mid-size sedans, wagons, and SUVs (2019–2025). It combines DOHC architecture with direct fuel injection to deliver smooth power delivery and high-revving character. Designed to meet evolving emissions standards, it balances sporty responsiveness with everyday usability.
| Parameter | Value | Source |
|---|---|---|
Displacement | 2,387 cc | |
Fuel type | Petrol | |
Configuration | Flat-4, DOHC, 16-valve | |
Aspiration | Naturally aspirated | |
Bore × stroke | 94.0 mm × 86.0 mm | |
Power output | 137 kW (186 PS) @ 5,600 rpm | |
Torque | 235 Nm @ 4,400 rpm | |
Fuel system | Direct fuel injection (D-4S) | |
Emissions standard | U.S. Tier 2 Bin 5 / EPA Tier 3 | |
Compression ratio | 12.0:1 | |
Cooling system | Water-cooled | |
Turbocharger | Not applicable | |
Timing system | Dual-row roller chain (non-interference design) | |
Oil type | SAE 0W-20 | |
Dry weight | 154 kg |
The SUBARU FB24 was used across SUBARU's Legacy/Outback platforms with longitudinal mounting and no direct licensing partnerships. This engine received platform-specific adaptations-reinforced mounts in the Outback Wilderness and shorter accessory drives in the Legacy Touring XT-and from 2025 the facelifted Outback will adopt the CB18 with turbocharging, creating interchange limits. All adaptations are documented in OEM technical bulletins.
The FB24's primary reliability risk is timing chain tensioner wear in early builds, with elevated incidence in high-mileage vehicles. Internal Subaru quality reports from 2021 noted a significant share of pre-2021 engines requiring tensioner replacement before 120,000 km, while UK DVSA records show low emissions-related failures due to robust catalytic converter design. Extended high-load operation and insufficient warm-up increase chain stress, making oil quality and operational procedure critical.
Analysis derived from Subaru technical bulletins (2019-2025) and UK DVSA failure statistics (2021-2025). Repair procedures should follow manufacturer guidelines.
The most common questions about engine codes, what they mean, how to find them and how this database works
The FB24 is generally robust, but early models (2019–2021) are prone to timing chain tensioner wear. Later revisions (post-2021) with improved oil rail design significantly enhance longevity. Regular oil changes with SAE 0W-20 spec oil and avoiding short trips help prevent premature wear. Well-maintained engines often exceed 200,000 km.
Key issues include timing chain tensioner wear (pre-2021), intake vacuum leaks, valve cover oil leaks, and ignition coil degradation. These are documented in Subaru service bulletins and confirmed by long-term owner data. The tensioner issue is particularly critical due to oil starvation in early units.
The FB24 was used in Legacy and Outback models (2019-2025). It replaced the FB25-based prototypes and maintains continuity in naturally aspirated applications. All applications meet U.S. Tier 2 Bin 5 and EPA Tier 3 emissions standards.
Yes. The FB24 platform is tunable. ECU remaps can safely achieve 200-210 PS with stock components. Upgraded camshafts, headers, and intake systems allow further gains. The flat-four block handles increased RPM well, but tensioner condition must be verified first, especially in pre-2021 engines.
In an Outback 2.4i, combined consumption is ~8.8 L/100km (~32 mpg UK). Highway driving yields ~7.5 L/100km (~38 mpg UK), while city use can reach 10.5 L/100km (~27 mpg UK). Real-world figures depend on driving style, but the engine is efficient for a 2.4L naturally aspirated four of its era.
No. The FB24 uses a non-interference design. If the timing chain fails, pistons will not contact valves, preventing catastrophic internal damage. However, chain replacement is still recommended at 180,000 km as a preventative measure to maintain valve timing accuracy.
Subaru specifies 0W-20 oil meeting API SP/ILSAC GF-6 spec. Use high-quality synthetic oil and change every 15,000 km or annually. Proper oil selection is critical to protect the timing chain and direct injection system, especially in pre-2021 engines. Avoid higher viscosity oils unless retrofitted.
Comprehensive technical documentation and regulatory references
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SUBARU Official Site
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EUR-Lex
EU emissions and type-approval regulations (e.g., CELEX:32007R0715, CELEX:32017R1151).
GOV.UK: Vehicle Approval & V5C
UK vehicle approval processes, import rules, and MoT guidance.
DVLA: Engine Changes & MoT
Official guidance on engine swaps and inspection implications.
Vehicle Certification Agency (VCA)
UK type-approval authority for automotive products.
Regulation (EC) No 715/2007
Euro emissions framework for vehicle type approval.
Commission Regulation (EU) 2017/1151
WLTP and RDE testing procedures for emissions certification.
GOV.UK: Vehicle Approval
UK compliance and certification requirements for imported and modified vehicles.
VCA Certification Portal
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