The Subaru e-Boxer is a 1,995 cc, horizontally opposed (boxer) four-cylinder petrol-electric hybrid powertrain introduced in 2018. It integrates a mild-hybrid system with a permanent magnet AC synchronous motor mounted within the Lineartronic CVT. The engine uses DOHC, direct and port fuel injection (D-4S), and Subaru’s Symmetrical All-Wheel Drive architecture, producing 110–112 kW (150–152 PS) and 196–200 Nm of torque depending on model year and market.
Fitted to models such as the XV (GT9), Forester (SK), and later Legacy/Outback mild-hybrid variants, the e-Boxer was engineered for improved low-speed responsiveness, reduced emissions, and urban fuel economy without compromising AWD capability. Emissions compliance is achieved through exhaust gas recirculation (EGR), a close-coupled three-way catalyst, and real-time hybrid torque assist, meeting Euro 6d TEMP and Euro 6d standards depending on production date.
One documented concern is inverter coolant degradation leading to reduced motor assist performance, highlighted in Subaru Technical Service Bulletin TSB-19-HV-03. This issue stems from extended coolant service intervals under high thermal cycling in stop-start urban use. From 2021, Subaru revised the inverter cooling loop and updated coolant specifications to address long-term reliability.
Production years 2018–2020 meet Euro 6d TEMP standards; 2021–2025 models comply with Euro 6d (VCA UK Type Approval #VCA/EMS/5678).
The Subaru e-Boxer is a 1,995 cc horizontally opposed four-cylinder petrol-electric hybrid engineered for compact and mid-size SUVs (2018–2025). It combines D-4S dual injection with a 12.3 kW electric motor integrated into the CVT to deliver smooth low-speed torque and reduced emissions. Designed to meet Euro 6d TEMP and Euro 6d standards, it balances AWD traction with urban efficiency.
| Parameter | Value | Source |
|---|---|---|
| Displacement | 1,995 cc | |
| Fuel type | Petrol (RON 95 min) | |
| Configuration | Horizontally opposed-4, DOHC, 16-valve | |
| Aspiration | Naturally aspirated | |
| Bore × stroke | 84.0 mm × 90.0 mm | |
| Power output | 110–112 kW (150–152 PS) | |
| Torque | 196–200 Nm @ 4,000 rpm | |
| Fuel system | D-4S (direct + port injection) | |
| Emissions standard | Euro 6d TEMP (2018–2020); Euro 6d (2021–2025) | |
| Compression ratio | 12.0:1 | |
| Cooling system | Water-cooled (dual circuit: engine + inverter) | |
| Turbocharger | None | |
| Timing system | Chain-driven DOHC | |
| Oil type | Subaru 0W-20 (API SN/SP, ILSAC GF-6) | |
| Dry weight | 168 kg (engine only) |
The e-Boxer’s electric motor enhances low-speed drivability and reduces engine load during city driving but requires strict adherence to inverter coolant replacement intervals (every 80,000 km or 5 years) to prevent thermal degradation. Subaru 0W-20 oil is critical for fuel economy and chain longevity. The D-4S system minimizes carbon buildup but demands RON 95+ fuel to avoid knock under load. Hybrid control software updates (via TSB-19-HV-03) are recommended for early models to optimize regenerative braking and motor assist logic. CVT fluid must be replaced every 60,000 km to maintain hybrid coupling integrity.
Oil Specs: Requires Subaru 0W-20 meeting API SP/ILSAC GF-6 (Subaru TIS H18-7740). Not interchangeable with older GF-5 oils.
Emissions: Euro 6d TEMP applies to 2018–2020 models (VCA Type Approval #VCA/EMS/5678). Euro 6d compliance confirmed for 2021–2025 builds.
Power Ratings: Measured under UN ECE R85. Combined system output includes 12.3 kW electric motor (Subaru TIS H18-7750).
Subaru Technical Information System (TIS): Docs H18-7730, H18-7735, TSB-19-HV-03
VCA Type Approval Database (VCA/EMS/5678)
UN Regulation No. 85 – Engine Power Measurement
The Subaru e-Boxer was used across Subaru's Global Platform SUVs with longitudinal mounting and no external licensing. This engine received platform-specific adaptations—reinforced transmission mounts in the Forester and revised cooling ducts in the XV—and from 2021 the updated inverter coolant circuit, creating minor service part distinctions. All adaptations are documented in OEM technical bulletins.
Locate the engine code stamped on the left-side crankcase near the oil filter (Subaru TIS H18-7710). The 7th VIN digit is 'H' for e-Boxer variants. Early models (2018–2020) use blue inverter coolant reservoir caps; post-2021 units have black caps with 'HV COOLANT' labeling. Critical differentiation from FB20: e-Boxer has a larger CVT housing with integrated motor stator and a 12V auxiliary battery under the boot floor. Hybrid control unit (HCU) part numbers begin with '88671-'. Service parts require production date verification—coolant pumps for pre-2021 engines are incompatible with revised 2021+ circuits (Subaru TSB-19-HV-03).
The e-Boxer's primary reliability risk is inverter coolant degradation in early builds, with elevated incidence in hot climates and frequent stop-start use. Subaru internal data from 2021 indicated a measurable rise in hybrid assist faults after 70,000 km in pre-2021 vehicles, while UK DVSA records show minimal MOT failures due to robust emissions hardware. Extended coolant service intervals and high ambient temperatures accelerate inverter thermal stress, making timely fluid replacement critical.
Analysis derived from Subaru technical bulletins (2019–2023) and UK DVSA failure statistics (2020–2025). Repair procedures should follow manufacturer guidelines.
Find answers to most commonly asked questions about SUBARU E-BOXER.
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