The 2008 inside diameter of a crush washer is 20+ mm sooooo...

Fairly certain its 20mm.

 

Here is the only ting I came up with, doesn't help much but does indicate it is a smaller thread then the previous years.

http://www.subaruforester.org/vbulletin/f66/2011-engine-oil-drain-threads-fumoto-valve-84298/

 

You mean the hex head size or the diameter of the shaft? Hex head takes a 17mm socket.

 

These look cool...and 16 mm according to site quickoildrainvalve.com/SearchResults.asp?Cat=40
Will have to get one after my "free" oil changes are up at 24,000 miles

 

Does anybody happen to know if it's 16 or 20mm crush washers? I'm planning on doing an oil change this weekend and it would be good to know what size to use.

Thanks!