Fresh Out of Outbacks!
The vin can decode it, and there are websites to do the lookup work for you. Have a google. You can also tell by looking at the car- H6 badges on the cars with the EZ30 flat 6, hood scoops and XT badges on the ones with the turbo flat 4, and cars with neither are the 2.5 NA flat four. These were the only 3 engines offered in the USA between 2005-2009.