It depends on what engine you have, the best way to know is to check the owners manual, but in case you don't have one for the 2.2 liter its 4.2qt and the 2.5 liter is 4.8qt
The gas tank on the 2009 Subaru Outback holds 16.9 gal..
The gas tank on the 2007 Subaru Outback holds 15.9 gal..
The gas tank on the 2008 Subaru Outback holds 16.9 gal..
The gas tank on the 2012 Subaru Outback holds 18.5 gal..
The gas tank on the 2004 Subaru Outback holds 16.9 gal..
The gas tank on the 2003 Subaru Outback holds 16.9 gal..
The gas tank on the 2002 Subaru Outback holds 16.9 gal..
The gas tank on the 2006 Subaru Outback holds 16.9 gal..
The gas tank on the 2013 Subaru Outback holds 18.5 gal..
The gas tank on the 2011 Subaru Outback holds 18.5 gal..
The gas tank on the 2014 Subaru Outback holds 18.5 gal..
The gas tank on the 2005 Subaru Outback holds 16.9 gal..