This 1,998 cc diesel is based on the Subaru 'Boxer Diesel' introduced in March 2008 - the world's first horizontally-opposed diesel engine for volume-produced passenger cars. It produces a maximum output of 150 ps and maximum torque of 350 Nm between 1,800 and 2,400 rpm.

For the 2011 Subaru Outback, this unique engine benefits from several technical refinements and enhanced environmentally-friendly features. The shape of the piston crowns has been changed for a wider, shallower design. This, in conjunction with improvements made to gas flow within the combustion chamber, have improved combustion efficiency and reduced the production of particulate matter. A 'lift sensor' has been added to the variable nozzle turbocharger for more precise control of the vanes.

The glow plugs have been changed from a metallic type to a ceramic type, raising the maximum operating temperature and providing better start-up at cold temperatures.

Control of the fuel injection has been optimised and the intake manifold has been redesigned in resin for improved airflow for improved torque characteristics and fuel efficiency. An added benefit of the new resin construction is the 1.5kg weight reduction over the previous aluminium version.

A single exhaust silencer has been used to optimise engine output and noise levels, while also saving weight. The addition of a vibration absorbing structure in the middle of main exhaust pipe also reduces noise levels.

The Subaru Boxer Diesel is fitted with a closed-type diesel particulate filter (DPF) that features a honeycomb shaped filter made of silicon carbide. The DPF, which is positioned low down with the turbocharger to maintain the car's low centre of gravity, improves engine combustion efficiency and reduces particulate matter in the exhaust, further enhancing environmental friendliness.

And finally, the exhaust gas recirculator (EGR) cooler has been enlarged to improve the system's efficiency by 12% - lowering NOx emissions to ensure that the new Outback complies with Euro 5 exhaust gas regulations.