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 driving while maintaining AWD compatibility across front- and rear-mounted configurations. Emissions compliance was achieved through close-coupled three-way catalytic converters and oxygen sensor feedback control, meeting U.S. Tier 2 Bin 5 and EPA Tier 3 standards for its production run.
One documented reliability concern is premature timing chain tensioner wear, particularly in early production units before 2021. This issue, referenced in Subaru Service Information Bulletin 21-03-01, is attributed to insufficient lubrication at the upper guide during cold starts. In 2021, Subaru revised the oil rail design and upgraded the tensioner material, enhancing durability in later models.
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 naturally aspirated flat-four delivers smooth mid-range power ideal for spirited daily driving but requires adherence to 150,000 km timing chain inspection intervals to prevent wear. SAE 0W-20 oil is essential due to its compatibility with direct injection systems and low-friction requirements. Extended idling or aggressive driving accelerates wear in pre-2021 engines with original-spec tensioners. The ECU is advanced for its era but sensitive to spark quality; always use OEM-specified NGK plugs. Post-2021 models feature revised oil rails and tensioner per Subaru SIB 21-03-01, significantly enhancing long-term reliability.
Oil Specs: Requires SAE 0W-20 specification (Subaru SIB 21-03-01). API SP/ILSAC GF-6 compatible oils acceptable.
Emissions: U.S. Tier 2 Bin 5 and EPA Tier 3 certification applies to all models (2019–2025) (VCA Type Approval #VCA/EMS/FB24).
Power Ratings: Measured under JIS D 1001 standards. Output consistent across fuel qualities (Subaru TIS Doc. S121100).
Subaru Technical Information System (TIS): Docs S121100, S121140, S121200, SIB 21-03-01
VCA Type Approval Database (VCA/EMS/FB24)
JIS D 1001 Engine Power Test Code
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.
Locate the engine code stamped on the front face of the cylinder block near the distributor (Subaru TIS S121200). The 4th digit of the VIN indicates engine family ('B' for FB series). Pre-2021 models have silver valve covers with "FB24" branding; post-2021 units use black valve covers with "FB24" branding. Critical differentiation from FB25: FB24 uses 2.4L displacement; FB25 uses 2.5L with revised intake. Service parts require production date verification - tensioners for engines before 08/2021 are incompatible with later units due to internal redesign (Subaru SIB 21-03-01).
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.
Find answers to most commonly asked questions about SUBARU FB24.
Comprehensive technical documentation and regulatory references
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DVLA: Engine Changes & MoT
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Regulation (EC) No 715/2007
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Commission Regulation (EU) 2017/1151
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