No longer is that true. At the 2007 Geneva Motor Show, Subaru unveiled the first diesel-fueled boxer engine for cars. Earlier this year, diesel-powered Subies started to appear in Europe and SmartPlanet has one of the first reviews of the new diesel powered Outback wagon. In their testing, the site recorded 40.6mpg (U.S.) in all around driving for the 4x4 Outback, a pretty impressive performance. They found the engine to be smooth running quiet, and refined. In fact, their only quibble was the car itself which is nearing the end of its lifecycle and is due for replacement in the next couple of years. We'll be getting the Subaru diesel in the U.S. market in 2010, perhaps just in time for a new Legacy/Outback.
[Source: SmartPlanet, thanks to Adam for the tip!]