What is the difference of an engine air filter and the cabin air filter for a 2007 Subaru outback?
The engine air filter is located above the engine and filters the incoming combustion air for the engine. These should be checked every oil change and depending on where and how you drive they should be replaced about every other to every third oil change or else bad gas mileage and poor engine performace will occur.
The cabin air filter removes dust and pollen from the air entering the interior of the car through the heating and air conditioning system when the control is set to "fresh air" or "outside air". This is less critical but will eventually be clogged and will need changing.
Also normally they are different styles of air filter so a different type for each one, your owners manual should tell you the types.
See this site for the cabin air filter: http://node28.wordpress.com/2009/07/13/replace-cabin-filter-07-outback/ (copy and paste into the browser window). The engine air filter is a bit of a joy as access is tight. The filter is in a housing by the left front wheel. There is a "scoop" intake manifold leading from the very front of the engine bay to the filter box. You need to undo the spring clips, pull back on the "upper" (back half) housing…