So, the 2.5L in my 2004 Outback is a 4, it's flat, and it's an opposed arrangement. It's a 16-valve (my 2004 is unless I'm reading wrong) but it's a SOHC. What are the advantages to this arrangement? This dopey question coming from a guy with DOHC 16-valve fours in an upright configurations all his life, including (especially, my C-14). Engineers are smarter than I, but looking under the hoods of these things, I can't fathom the extra complexity and especially, the "why" of it. What is gained? Something HAS to be gained, I'm sure there is a body of thought behind it, but comparisons aren't to be found on the web, or not easily.