Dennis (bluesubie) -
I disagree with you slightly. Here's why:
He's got a high mileage 2.0 liter...which tells me two things:
1. Almost all clogged banjo bolt filters happen with 2.5 liter engines AFAIK. Correct me if I'm wrong.
2. At this mileage, as long as the engine is in a good state of tune it's much less likely to be throwing off sufficient gunk to clog the filter.
No one has been able to explain to me how a shorter oil change would help prevent the banjo bolt filter from getting clogged unless the oil is breaking down (i.e. sludging). And that's not happening on a PAO oil in 8,000 miles (compared to Dino oil in 3750 miles). A shorter oil change to prevent a clogged banjo bolt filter only makes sense when it's combined with an oil that is actively breaking down at that mileage. And I personally feel that' snot going to happen in a near-stock car running AMSOIL ASL (or many other robust oils).
Here's a legacy gt owner who runs AMSOIL SSO for 16k/1 year:
http://www.legacygt.com/forums/showthread.php?t=75949&highlight=AMSOIL
Subaru, as far as I can tell, reduced the oil change interval because a Dino 5w30 could not withstand 7500 miles in these engines, consistently, without severely shearing and breaking down. And they changed the interval once the 2.5 liter turbos were used in everything (legacy, WRX, Sti, Forester, Outback).
I don't want to make a recommendation out of ignorance, but the reasons above combined with my modest knowledge of synthetics leads me to believe that in a higher-mileage, well maintained 2.0 liter WRX you could run AMSOIL ASL 5w30 for 8k (after showing it's rock solid at 4k) without a problem, providing good air and oil filtration are in use.
Just my .02, but I appreciate that there are differing opinions on here. Once my Leggy is out of warranty, I'll switch to running 7500 mile (minimum) intervals on a good quality synthetic.
Joe