Subaru EE20 (boxer diesel)

2.0 L · flat-4 · turbocharged · diesel · 2008–present

Also known as: ee20, ee20z, subaru boxer diesel, boxer diesel

Subaru's 2.0 boxer diesel — the first horizontally opposed diesel fitted to a passenger car — in the Impreza, Legacy, Outback, Forester and XV.

The layout is the reason it exists and the reason it is difficult. A flat engine is short and low, which suits Subaru's symmetrical drivetrain; but a diesel's combustion pressures in a flat layout put unusual loads through the crankshaft, and the crankshaft is this engine's known weakness. Failures are not common but they are catastrophic when they happen, and they concentrate on high-mileage examples driven hard from cold.

Its everyday faults are the ordinary modern-diesel ones and they are worse here than most: the DPF suffers badly on short journeys because the engine takes a long time to reach temperature, and an interrupted regeneration puts fuel into the sump — an oil level that has RISEN on the dipstick is the tell, and continuing to drive on diluted oil is what leads to the bearing failures the engine is known for.

So the crankshaft reputation and the DPF story are the same story, which is worth stating plainly: most of what kills these is a use pattern rather than a design fault.

Cars fitted with this engine

11 generations, across 1 make. From the authored catalogue — an absent car means the catalogue has not reached it, not that the engine was never fitted.

Subaru

Information, not instruction

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The car — make, model, year and engine. The same fault behaves differently on each.
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