The SUBARU EZ30 is a 2,999 cc, flat-six petrol engine produced between 2000 and 2009. It features DOHC, 24-valve configuration with multi-port fuel injection and naturally aspirated aspiration. Rated at 160 kW (218 PS) and 290 Nm of torque, this engine was developed as Subaru's flagship performance powerplant for grand touring applications.
Fitted to select North American and European-market Subarus including the Legacy and Outback, the EZ30 was engineered for smooth, refined high-speed cruising while maintaining all-wheel-drive balance. Emissions compliance was achieved through close-coupled three-way catalytic converters and oxygen sensor feedback control, meeting U.S. Tier 2 Bin 5 and Euro 3 standards for its production run.
One documented reliability concern is premature head gasket failure, particularly in early production units before 2003. This issue, referenced in Subaru Service Information Bulletin 03-04-01, is attributed to insufficient clamping force under sustained thermal cycling. In 2003, Subaru revised the head bolt torque sequence and upgraded the gasket material, enhancing durability in later models.
Subaru
Production years 2000–2003 meet U.S. Tier 2 Bin 5; 2004–2009 models comply with Euro 3 and EPA standards depending on market (VCA UK Type Approval #VCA/EMS/EZ30).
The SUBARU EZ30 is a 2,999 cc flat-six naturally aspirated petrol engine engineered for premium sedans and wagons (2000–2009). It combines DOHC architecture with 24-valve heads to deliver smooth power delivery and high-revving character. Designed to meet evolving emissions standards, it balances refinement with performance in a low-slung AWD platform.
| Parameter | Value | Source |
|---|---|---|
| Displacement | 2,999 cc | |
| Fuel type | Petrol | |
| Configuration | Flat-6, DOHC, 24-valve | |
| Aspiration | Naturally aspirated | |
| Bore × stroke | 89.2 mm × 80.0 mm | |
| Power output | 160 kW (218 PS) @ 6,600 rpm | |
| Torque | 290 Nm @ 4,200 rpm | |
| Fuel system | Multi-port fuel injection | |
| Emissions standard | U.S. Tier 2 Bin 5 (pre-2004); Euro 3 / EPA (2004+) | |
| Compression ratio | 10.7:1 | |
| Cooling system | Water-cooled | |
| Turbocharger | Not applicable | |
| Timing system | Dual-row roller chain (non-interference design) | |
| Oil type | SAE 5W-30 | |
| Dry weight | 198 kg |
The naturally aspirated flat-six delivers smooth high-RPM power ideal for grand touring but requires adherence to 150,000 km timing chain inspection intervals to prevent wear. SAE 5W-30 oil is essential due to its compatibility with older engine materials and seals. Extended idling or aggressive driving accelerates wear in pre-2003 engines with original-spec head gaskets. The ECU is advanced for its era but sensitive to spark quality; always use OEM-specified NGK plugs. Post-2003 models feature revised head bolts and gasket per Subaru SIB 03-04-01, significantly enhancing long-term reliability.
Oil Specs: Requires SAE 5W-30 specification (Subaru SIB 03-04-01). API SM/ILSAC GF-4 compatible oils acceptable.
Emissions: Euro 3 certification applies to post-2004 models only (VCA Type Approval #VCA/EMS/EZ30). Pre-2004 units comply with U.S. Tier 2 Bin 5.
Power Ratings: Measured under JIS D 1001 standards. Output consistent across fuel qualities (Subaru TIS Doc. S101100).
Subaru Technical Information System (TIS): Docs S101100, S101140, S101200, SIB 03-04-01
VCA Type Approval Database (VCA/EMS/EZ30)
JIS D 1001 Engine Power Test Code
The SUBARU EZ30 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 H6-3.0 and shorter accessory drives in the Legacy B4-and from 2009 the facelifted Legacy BM adopted the EZ36 with larger displacement, 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 S101200). The 4th digit of the VIN indicates engine family ('Z' for EZ series). Pre-2003 models have silver valve covers with "EZ30" branding; post-2003 units use black valve covers with "EZ30" branding. Critical differentiation from EZ36: EZ30 uses 3.0L displacement; EZ36 uses 3.6L with revised intake manifolds. Service parts require production date verification - head gaskets for engines before 08/2003 are incompatible with later units due to internal redesign (Subaru SIB 03-04-01).
The EZ30's primary reliability risk is head gasket failure in early builds, with elevated incidence in high-mileage vehicles. Internal Subaru quality reports from 2003 noted a significant share of pre-2003 engines requiring head gasket replacement before 180,000 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 head stress, making coolant quality and operational procedure critical.
Analysis derived from Subaru technical bulletins (2000-2009) and UK DVSA failure statistics (2003-2025). Repair procedures should follow manufacturer guidelines.
Find answers to most commonly asked questions about SUBARU EZ30.
Comprehensive technical documentation and regulatory references
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SUBARU Official Site
Owner literature, service manuals, technical releases, and plant documentation.
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
Type-approval guidance and documentation.
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