Subaru EJ25 Engine for Sale | OEM Used Subaru EJ25 2.5 Liter

Subaru's 2.5L horizontally-opposed boxer-4 engine from the EJ engine family. The Subaru EJ25 is Subaru's 2.5L boxer-4 engine from the long-running EJ engine family, serving as Subaru's mainstream and performance engine across Impreza, Legacy, Outback, Forester, WRX, and STI (in some markets) applications from approximately 1996 through 2018. The horizontally-opposed boxer-4 configuration is Subaru's signature engine design, providing a low center of gravity that benefits handling balance. CRITICAL distinction: the EJ25 is offered in naturally-aspirated (NA) and turbocharged variants with substantially different characteristics; specifying turbo vs non-turbo is essential before ordering. Specifications: 2.5 liters displacement (2,457 cc), horizontally-opposed boxer-4 (180-degree opposed), bore x stroke 99.5 mm x 79 mm, SOHC or DOHC depending on variant, aluminum block, AVCS variable valve timing on DOHC turbo and later SOHC variants, port fuel injection, timing belt driven.

Substantially different engines that cannot be cross-applied. The NA EJ25 and Turbo EJ25 variants share the EJ25 base architecture but are NOT interchangeable. Key differences: compression ratio ~10:1 NA vs ~8.4:1 Turbo (installing NA pistons in turbo application causes destructive detonation; installing turbo pistons in NA application reduces power). Cylinder head: SOHC (most NA) vs DOHC (turbo) (not cross-compatible due to different camshaft, valve, and timing belt arrangements). ECU calibration: Turbo ECU expects boost pressure inputs; NA ECU does not have turbo control logic. Fuel system: Turbo requires higher-flow injectors and fuel pump. Cooling capacity: Turbo applications have larger radiator, intercooler, oil cooler. Internal components: Turbo variants may have forged pistons, stronger rods, reinforced block (semi-closed deck on EJ257). Specify turbo vs non-turbo when ordering.

Well-documented head gasket concern requiring honest disclosure. The Subaru EJ25 has well-documented head gasket concerns. SOHC NA EJ25 (Phase II 1999-2010): external head gasket leak pattern (coolant leaks externally from head gasket); head gasket replacement is a common service item. DOHC Turbo EJ25: internal head gasket failure pattern (coolant intrusion into combustion chamber); less common than SOHC NA head gasket leak, but more severe when it occurs. Aftermarket multi-layer steel (MLS) head gaskets: common upgrade during head gasket replacement to extend service life. Cylinder head retorque: some Subaru technicians recommend cylinder head retorque at specific intervals to extend head gasket life. Head gasket condition is assessed on every used EJ25 engine before sale, and we honestly disclose findings. Buyers should budget $1,500-3,000 for proactive head gasket replacement with MLS gaskets at acquisition if the existing gaskets are at high mileage.

EJ255 for WRX and EJ257 for STI with different performance levels. EJ255 (WRX Turbo): 224-265 HP at 5,200-6,000 RPM, DOHC, AVCS, used in Subaru WRX Turbo applications. EJ257 (STI Turbo): 293-310 HP at 6,000-6,400 RPM, DOHC, AVCS, semi-closed deck block, forged pistons in some variants, used in Subaru STI applications. Both variants use compression ratio approximately 8.4:1 (lower compression to allow boost). Turbocharger: IHI VF-series turbo (varying versions across WRX / STI applications). Applications: EJ255 in WRX Turbo / Legacy GT Turbo / Forester XT / Outback XT; EJ257 in STI specifically (the higher-performance variant). The EJ255 and EJ257 are not directly interchangeable due to different block specifications, ECU calibration, and internal components, though they share the EJ25 boxer-4 architecture.

Four Subaru boxer engine listings. The Subaru EJ25 (this listing) is the mainstream 2.5L variant of the EJ engine family. The Subaru FA20 engine is the modern Subaru / Toyota co-developed FA family 2.0L boxer with FA20D NA for BRZ / 86 / FR-S and FA20DIT turbo for WRX 2015 plus (the modern successor to EJ25 in WRX applications and represents Subaru's transition to direct injection). The Subaru 2.5 overview engine covers the broader 2.5L Subaru boxer family. The Subaru EJ253 engine covers the SOHC NA EJ253 variant specifically. Four Subaru boxer engine listings across : (this listing) EJ25 turbo and non-turbo with critical distinction, FA20 modern Subaru / Toyota co-developed direct-injection boxer, Subaru 2.5 overview, EJ253 SOHC NA specifically.

Head gasket the primary concern plus other documented modes. Head gasket failure: documented Subaru EJ25 concern (SOHC NA external leak pattern, DOHC turbo internal leak pattern); primary maintenance / repair item. Timing belt wear: every 105,000 miles maintenance critical; failure damages interference engine. Spark plug access: spark plug access on horizontally-opposed boxer is more difficult than inline engines; budget extra labor for plug service. Knock sensor failure: common cause of check engine codes. AVCS solenoid wear: DOHC variants. Turbocharger wear (turbo variants): IHI VF-series turbo can wear at high mileage; turbo failure on WRX / STI applications is well-documented at 100,000-150,000 miles depending on maintenance. Oil consumption with age: some EJ25 examples exhibit elevated oil consumption past 100,000 miles.

Head gasket assessment, timing belt, spark plugs, turbo inspection (turbo variants). After acquiring a used EJ25 engine, budget for these items. Head gasket assessment: budget $1,500-3,000 for proactive MLS head gasket replacement at acquisition if existing gaskets are at high mileage (recommended for high-mileage EJ25 examples given documented concern). Timing belt service: budget $800-1,500 for full timing belt service including water pump, tensioner, idler pulleys; every 105,000 miles is critical. Spark plug replacement: budget $200-400 (labor is higher than inline engines due to boxer access). Knock sensor inspection: replace if codes present. Turbo inspection (turbo variants): budget $1,500-3,500 for turbo replacement if turbo is at high mileage. Strict synthetic oil maintenance: 3,750-5,000 mile intervals (NA), 3,000-3,750 mile intervals (turbo); use Subaru-approved synthetic oil. Quality 91 octane fuel minimum for turbo variants.

No. There is no core return required.