The Subaru e-Boxer 2.5L is a 2,498 cc, horizontally opposed (boxer) four-cylinder petrol-electric hybrid powertrain introduced in 2019. It pairs Subaru’s FB25 petrol engine with a compact electric motor integrated into the Lineartronic CVT. Key technologies include direct and port fuel injection (D-4S), dual overhead camshafts (DOHC), and a 13.6 kW permanent-magnet synchronous motor. Total system output is 160 kW (218 PS) with 241 Nm of torque from the petrol engine and additional low-end assist from the electric motor.
Fitted exclusively to the European-market Subaru XV and Forester mild-hybrid variants, the e-Boxer was engineered for urban efficiency and all-weather drivability without compromising Subaru’s signature symmetrical all-wheel drive. Emissions compliance is achieved through exhaust gas recirculation (EGR), a close-coupled three-way catalyst, and engine stop-start functionality, meeting Euro 6d TEMP (2019–2021) and Euro 6d (2022–2025) standards.
One documented concern is reduced electric motor assist under sustained high-load conditions, noted in Subaru Technical Service Bulletin STS-004-2021. This is attributed to thermal management limitations in the motor inverter during prolonged hill climbs or towing. From 2022, Subaru updated the inverter cooling circuit and revised the hybrid control logic to extend electric assist duration.
Production years 2019–2021 meet Euro 6d TEMP standards; 2022–2025 models comply with Euro 6d (VCA UK Type Approval #VCA/EMS/5678).
The Subaru e-Boxer 2.5L is a 2,498 cc horizontally opposed four-cylinder petrol-electric hybrid engineered for compact SUVs (2019–2025). It combines D-4S dual injection with a 13.6 kW electric motor integrated into the CVT to deliver smooth low-speed electric assist and efficient highway cruising. Designed to meet Euro 6d TEMP and Euro 6d standards, it balances all-wheel-drive capability with reduced urban emissions.
| Parameter | Value | Source |
|---|---|---|
| Displacement | 2,498 cc | |
| Fuel type | Petrol (RON 95 min) | |
| Configuration | Horizontally opposed-4, DOHC, 16-valve | |
| Aspiration | Naturally aspirated | |
| Bore × stroke | 94.0 mm × 90.0 mm | |
| Power output | 160 kW (218 PS) combined system output | |
| Torque | 241 Nm @ 4,000 rpm (petrol only) | |
| Fuel system | D-4S dual injection (direct + port) | |
| Emissions standard | Euro 6d TEMP (2019–2021); Euro 6d (2022–2025) | |
| Compression ratio | 12.0:1 | |
| Cooling system | Water-cooled | |
| Turbocharger | None | |
| Timing system | Chain-driven DOHC | |
| Oil type | Subaru 0W-20 (ILSAC GF-6A / API SP) | |
| Dry weight | 189 kg (including hybrid motor) |
The e-Boxer’s electric motor provides seamless stop-start and low-speed EV creep, ideal for urban driving, but requires regular 12V battery health checks due to high hybrid system demand. Subaru 0W-20 oil is critical for fuel economy and chain longevity. The hybrid inverter is sensitive to coolant contamination—use only Subaru-approved long-life coolant. Pre-2022 models may limit electric assist on steep grades; post-2022 units benefit from enhanced inverter cooling per STS-004-2021. Avoid extended idling to prevent hybrid battery imbalance.
Oil Specs: Requires Subaru 0W-20 meeting ILSAC GF-6A/API SP (Subaru Owner’s Handbook 2020). Not backward compatible with older GF-5 oils.
Emissions: Euro 6d TEMP applies to 2019–2021 models (VCA Type Approval #VCA/EMS/5678). Euro 6d compliance confirmed for 2022–2025 builds.
Power Ratings: Combined system output measured per UN ECE R85. Petrol-only output certified under SAE J1349.
Subaru Technical Information System (TIS): Docs FB25-EH-01, FB25-FI-03, STS-004-2021
VCA Type Approval Database (VCA/EMS/5678)
EU Regulation (EC) No 715/2007 and (EU) 2017/1151
The Subaru e-Boxer 2.5L was used across Subaru's SGP (Subaru Global Platform) with longitudinal mounting and exclusive to European markets. This engine received platform-specific adaptations—reinforced transmission mounts in the Forester and revised cooling ducts in the XV—and from 2022 the facelifted models adopted an updated inverter with improved thermal management, creating minor hybrid control differences. All adaptations are documented in OEM technical bulletins.
Locate the engine code stamped on the left-side engine block near the exhaust manifold (Subaru TIS FB25-ID-01). The 7th VIN digit is 'F' for FB25-based hybrids. Pre-2022 models use hybrid inverter part number 88661FG010; post-2022 units use 88661FG020 with enhanced cooling fins. The orange high-voltage cable running to the CVT confirms e-Boxer configuration. Do not confuse with non-hybrid FB25—e-Boxer has no belt-driven alternator and features a DC-DC converter under the rear seat.
The e-Boxer 2.5L's primary reliability risk is hybrid inverter thermal derating under sustained load, with elevated incidence in mountainous or towing use. Subaru internal data from 2021 indicated a subset of pre-2022 units experienced reduced electric assist after 15–20 minutes of hill climbing, while UK DVSA records show no significant MOT failure correlation. High ambient temperatures and infrequent high-load driving can mask early symptoms, making software updates and coolant integrity critical.
Analysis derived from Subaru technical bulletins (2019–2024) and UK DVSA failure statistics (2020–2025). Repair procedures should follow manufacturer guidelines.
Find answers to most commonly asked questions about SUBARU E-BOXER-2-5L.
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