Also known as: ej20, ej25, ej205, ej257, 2.0 boxer turbo, sti engine, wrx engine, ej253, ej22, ej22t, ej20t, ej255, ej15, ej16, ej18, ej204, ej207, ej251, el15
The flat-four that defined Subaru for thirty years — naturally aspirated in the Impreza and Forester, and turbocharged in the WRX and STI, where it became one of the most modified engines in the world.
Head gasket failure is the fault the family is known for, particularly on the 2.5 naturally aspirated versions of the late 1990s and 2000s. The presentation is often external — coolant or oil weeping at the side of the block — rather than the classic mayonnaise-under-the-cap, so the layout changes what the symptom looks like.
On the turbocharged versions the additional and more expensive theme is ringland failure, where detonation damages the piston between the ring grooves. It is strongly associated with modification, poor fuel and heat, and it presents as a sudden misfire with low compression on one cylinder. Because these engines are modified so routinely, establishing what boost and software the car is running is the first question on any knock or misfire complaint, ahead of any component test.
It is a family spanning 1.5 to 2.5 litres, and the cars listed below carry the EJ15, EJ16, EJ18, EJ20, EJ22 and EJ25 between them. The head-gasket reputation belongs to the 2.5 naturally aspirated engines and the ringland failures to the turbocharged 2.0 — so a fault quoted for the EJ is almost always a fault quoted for one member of it.
Cars fitted with this engine
18 generations, across 2 makes. From the authored catalogue — an absent car means the catalogue has not reached it, not that the engine was never fitted.
Subaru
- Legacy BC 1989–1994
- Impreza GC and GF 1992–2000
- Legacy BD 1993–1999
- Forester SF 1997–2002
- Legacy BE 1998–2003
- Impreza GD 2000–2007
- Forester SG 2002–2008
- Baja BT 2002–2006
- Outback BP 2003–2009
- Legacy BL 2003–2009
- Impreza GE 2007–2011
- Forester SH 2008–2012
- Outback BR 2009–2014
- Legacy BM 2009–2014
- Outback BS 2014–2019
- WRX VA 2014–2021
- Legacy BN 2014–2019
Information, not instruction
CarGeek is a reference, not a service manual. Its pages are written from public sources and from what other people have found, never from a manufacturer's own service information, so they can be wrong or incomplete for your particular vehicle. Some of what they describe carries real risk: high voltage, fuel under pressure, stored energy, hot and moving parts.
Have anything you intend to act on checked by a trained person against the manufacturer's own procedure for your vehicle. Nothing here replaces that procedure.
Posted about this engine
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Nothing posted about this yet. Whatever you found is worth writing down — even a dead end saves someone the same afternoon.
What makes one worth reading:
- The car — make, model, year and engine. The same fault behaves differently on each.
- What you measured, not only what you replaced.
- What actually fixed it — or that nothing did, which is worth knowing too.
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